UC-NRLF 


FROM  THE  LIBRARY  OF 
WILLIAM  A.  SETCHELL,i864-i943 

PROFESSOR  OF  BOTANY 


DEPARTMENT  OF  THE  INTERIOR -U.  S.  GEOLOGICAL  SURVEY 
,T.  W.  POWELL,  DIRECTOR 


THE    FORMATION 


OF 


TRAVERTINE  AND  SILICEOUS  SINTER 


BY  THK 


VEGETATION  OF  HOT  SPRINGS 


WALTER  HAKVEY  WEED 


EXTRACT  FROM  THE  NINTH  ANNUAL  REPORT  OF  THE  DIRECTOR,  1887-' 


WASHINGTON 

GOVERNMENT  FEINTING  OFFICE 
1890 


B10LO«Y 
LIBRARY 


FORMATION  OF  TRAVERTINE  AND  SILICEOUS  SINTER  BY  THE 
VEGETATION  OF  HOT  SPRINGS. 

BY 

WALTER  HARVEY  WEED. 


613 


OOLOGY  LIBRARY 


CONTENTS. 


Paga 

Introduction 619 

Plants  as  rock-builders 619 

Vegetation  of  hot  waters 620 

Hot  springs  of  the  Yellowstone  National  Park 628 

Mammoth  Hot  Springs 628 

Geological  relations 629 

Travertine  deposits " 629 

The  springs  and  their  vegetation. 630 

General  occurrence  of  the  algae 631 

Effect  of  environment 633 

Description  of  the  vegetable  growth. 635 

Solubility  of  carbonate  of  lime 637 

Character  of  the  hot  spring  waters 638 

Deposition  of  carbonate  of  lime 640 

Deposits  of  carbonate  of  lime  due  to  plant  life 642 

Description  of  the  deposits 645 

Weathering  of  the  travertine ~. 649 

Origin  of  siliceous  sinter 650 

Upper  Geyser  Basin  of  the  Firehole  River 651 

General  description 651 

Character  of  the  hot  spring  waters 654 

Formation  of  siliceous  sinter 655 

Algous  vegetation  of  the  hot  waters 657 

Algae  pools  and  channels 658 

Fibrous  varieties  of  algous  sinter 665 

Rate  of  deposition  of  siliceous  sinter 666 

Microscopic  evidence 667 

Moss  sinter — 667 

Diatom  beds. 668 

Nature  of  siliceous  sinter 669 

Siliceous  sinters  from  New  Zealand 672 

Summary 676 

615 


ILLUSTRATIONS. 


PLATE  LXXVIII.  Terraced  basins  of  Blue  Springs,  Mammoth  Hot  Springs.  628 

LXXIX.  Marble  basins,  Mammoth  Hot  Springs  632 

LXXX.  Pulpit  basins,  Mammoth  Hot  Springs 636 

LXXXI.  Travertine,  Mammoth  Hot  Springs 648 

LXXXII.  Algae  channels,  Emerald  Spring,  Upper  Geyser  Basin 656 

LXXXIII.  Algae  basin,  Eftnerald  Spring,  Upper  Geyser  Basin 658 

LXXXIV.  Upper  algae  basin,  Jelly  Spring,  Lower  Geyser  Basin 660 

LXXXV.  Middle  algae  basin,  Jelly  Spring,  Lower  Geyser  Basin 662 

LXXXVI.  Stony  forms,  Jelly  Spring,  Lower  Geyser  Basin 664 

LXXXVII.  Sinter  forms  from  algae  basins 666 

FlG.  52.  Travertine  fan,  Main  terrace,  Mammoth  Hot  Springs 632 

53.  Coating  specimens,  Mammoth  Hot  Springs 634 

54.  General  view  of  part  of  Upper  Geyser  Basin 652 

55.  Avoca  Spring,  Upper  Geyser  Basin 654 

56.  Algae  forms,  Lower  Geyser  Basin - 663 

617 


FORMATION  OF  TRAVERTINE  AND  SILICEOUS  SINTER  BY  THE 
VEGETATION  OF  HOT  SPRINGS. 


BY  WALTER  HARVEY  WEED. 


INTRODUCTION. 

Among  the  many  interesting  natural  phenomena  that  claim  the 
attention  of  the  visitor  to  the  Yellowstone  National  Park,  the  geysers 
and  hot  springs  rank  first  in  general  interest.  Their  novelty  and 
beauty  are  sure  to  attract  universal  admiration,  while  the  vast  quan- 
tities of  hot  water  that  flow  from  the  ground  are  convincing  evidences 
of  the  nearness  of  internal  heat.  These  steaming  fountains  and  boil- 
ing pools  are  usually  surrounded  by  snowy  white  borders  of  mineral 
matter  deposited  by  the  hot  waters.  At  the  Mammoth  Hot  Springs 
this  consists  of  carbonate  of  lime,  that  forms  the  unique  marble  ter- 
races and  pulpit  basins  of  those  springs.  (PI.  LXXIX.)  At  the 
Geyser  basins  the  waters  deposit  silica,  that  forms  the  fretted  rims 
of  the  pools  and  the  beautifully  beaded  and  coral-like  deposits  of 
the  cones,  and  covers  large  areas  of  ground  about  the  springs  with 
a  sheet  of  white  and  glaring  sinter.  Not  only  are  the  occurrence  and 
the  nature  of  these  deposits  such  as  make  them  of  interest  to  every 
visitor,  but  the  problem  of  their  origin  has  proved  to  be  one  of  the 
prominent  features  in  the  scientific  investigation  of  the  hydrother- 
mal  phenomena  of  the  park,  as  it  has  been  found  that  such  deposits 
are  very  largely  due  to  the  growth  and  life  of  a  brilliant  colored 
algous  vegetation,  living  in  the  hot  mineral  waters. 

PLANTS  AS  ROCK-BUILDERS. 

A  review  of  the  various  geologic  agents  that  have  built  up  the 
strata  forming  the  earth's  crust  shows  that  living  organisms  have 
taken  an  important  part  in  rock  formation.  The  abundance  of  their 
remains  in  ancient  as  well  as  the  most  recently  formed  sediments 
shows  that  the  corals  and  mollusks  of  all  periods  have  been  active 
rock-builders.  The  geological  work  executed  by  such  forms  of  animal 
life  is  therefore  quite  apparent  to  the  students  of  nature.  On  the 
contrary,  the  geological  work  of  plant  life  has  not  been  generally  rec- 
ognized, partly  because  it  is  less  conspicuous,  and  partly  because 
the  absence  of  organic  remains  in  many  deposits  formed  in  this  way 
has  prevented  a  recognition  of  the  true  origin  of  the  rocks. 

619 


620  FORMATION    OF    HOT    SPRING    DEPOSITS. 

It  has  been  proved  that  living  plants  further  geologic  change  in 
several  ways;  by  promoting  the  disintegration  and  decay  of  existing 
rocks,  by  building  up  new  rock  formations,  and,  upon  their  death,  by 
starting  a  series  of  changes  resulting  from  the  action  of  the  decay- 
ing vegetable  matter  upon  various  mineral  substances.  New  forma- 
tions are  built  up  by  living  plants  in  two  ways — by  the  accumulation 
of  their  plant  remains  and  by  the  chemical  reactions  resulting  from 
the  growth  and  life  of  the  plants:  in  either  case  mineral  matter  is  de- 
posited. Where  the  mineral  matter  preserves  the  form  and  struct- 
ure of  the  plant,  as  is  the  case  with  the  silica  forming  the  well-known 
beds  of  diatomaceous  earth,  the  origin  of  the  deposit  is  apparent,  but 
in  many  cases  no  trace  of  plant  structures  can  be  distinguished,  even 
when  thin  sections  of  rocks  that  are  undoubtedly  formed  by  plants 
are  seen  under  the  microscope.  This  is  true  of  some  marine  lime- 
stones formed  by  calcareous  algse,  and  is  especially  true  of  several 
classes  of  deposits  heretofore  considered  to  have  a  purely  chemical 
origin,  such  as  travertine,  siliceous  sinter,  certain  gypsums  and 
iron  ores.  In  such  cases  it  is  only  by  a  careful  study  of  the  actual* 
process  of  formation  of  the  deposits  that  we  can  tell  with  certainty 
their  true  manner  of  formation.  This  has  been  done  in  the  case  of 
the  deposits  formed  about  the  hot  springs  and  geysers  of  the  Yellow- 
stone Park,  and  it  is  the  purpose  of  the  present  paper  to  show  the 
origin  and  manner  of  formation  of  these  interesting  mineral  deposits. 

VEGETATION  OF  HOT  WATERS. 

The  presence  of  organic  life  in  highly  heated  mineral  waters  is  a 
subject  of  considerable  interest  not  only  to  students  of  biology,  but 
to  geological  observers  as  well.  It  shows  the  development  of  life 
under  very  adverse  conditions  of  temperature,  and  affords  an  oppor- 
tunity for  the  study  of  the  modifying  effect  of  high  temperatures 
and  chemical  solutions  upon  forms  found  also,  in  ordinary  surface 
waters.  The  ability  of  life  to  withstand  such  extreme  conditions 
shows  the  possible  existence  of  such  forms  in  the  early  history  of 
the  earth,  when  the  crust  is  supposed  to  have  been  covered  by  highly 
heated  mineralized  water.  Thus  far  this  subject  has  received  but 
little  attention,  and  the  data  accessible  are  meager  and  unsatisfac- 
tory, this  being  especially  true  of  the  animal  life  of  hot  waters. 

The  vegetation  of  hot  springs  consists  entirely  of  various  species 
of  fresh  water  algae,  flowerless  cryptogarnic  plants,  closely  related 
to  the  salt  water  algse  or  sea- weeds.  The  fresh  water  species  are 
less  striking  and  varied  than  the  marine  growths,  and  are  generally 
composed  of  green  thread-like  structures  of  more  or  less  slimy  con- 
sistency. '  It  is  well  known  that  algae  are  abundant  in  the  hot  waters 
of  many  and  widely  separated  localities,  for,  in  the  various  works  of 

'Phycology:  Prof.  Farlow,  in  Johnson's  Encyclopedia. 


WEED.]  VEGETATION    OF    HOT    WATERS.  621 

i 

travel  and  exploration  in  which  the  occurrence  of  hot  springs  has 
been  described,  mention  is  frequently  made  of  bright  green  confervas 
living  in  the  hot  pools  and  streams.  Where  the  plants  present  in 
thermal  waters  are  of  this  color  their  vegetable  nature  seems  to  have 
been  readily  recognized,  but  there  is  reason  to  believe  that  the  exist- 
ence of  algae  of  other  colors,  such  as  the  red  and  yellow  species  com- 
mon in  the  Yellowstone  springs,  has  generally  been  overlooked  or 
the  growth  mistaken  for  mineral  matter.  This  is  not  surprising,  as 
the  plants  are  often  incrusted  and  hidden  by  mineral  material  de- 
posited by  the  hot  water,  and  the  organic  nature  of  the  substance  is 
often  scarcely  recognizable  even  by  botanists.  Thus  in  sulphur 
waters  the  algae  are  very  generally  incrusted  by  grains  of  sulphur,  or 
are  inclosed  in  gypsum,  while  the  vegetation  of  calcareous  springs 
is  often  buried  in  travertine  deposited  by  the  water,  only  the  grow- 
ing tips  of  the  plants  being  free.  Similarly,  the  threads  of  algae  liv- 
ing in  ferruginous  waters  are  incrusted  by  oxide  of  iron,  while  in 
siliceous  waters  such  growths  are  inclosed  in  gelatinous  silica. 

In  reviewing  the  literature  of  this  subject,  vegetation  is  found  to 
be  a  common  accompaniment  of  thermal  springs  in  all  parts  of  the 
world,  but,  although  the  presence  of  these  hot-water  growths  has. 
been  recognized,  the  conditions  under  which  they  exist  are  rarely 
given  and  the  plants  themselves  have  been  studied  and  identified  at 
very  few  localities.  Of  these  the  foremost  is  Carlsbad,  Bohemia. 
Its  hot  springs  have  long  been  noted  for  their  curative  properties, 
and  thus  they  attracted  the  attention  of  scientific  men  at  an  early 
date.  In  1827,  Agardth  described  the  algous  growths  of  these  ther- 
mal waters,1  and  the  botanist  Corda2  figured  and  described  species 
from  these  springs  in  1835.  Schwabe  published  a  paper  in  1837 3  in 
which  he  describes  the  occurrence  of  the  algae,  giving  the  tempera- 
tures at  which  the  different  species  were  found,  besides  figuring  and 
describing  the  plants  themselves.  The  most  important  paper,  from 
a  geological  stand-point,  is,  however,  that  published  by  Prof.  Ferd. 
Cohn  in  1862, 4  in  which  the  physiological  action  of  the  plant  life  is 
shown  to  cause  the  deposition  of  travertine  by  the  hot  waters. 

Algae  from  the  hot  springs  of  Italy  were  described  by  Meneghine  * 
in  1842,  and  Ehrenberg  says'  that  algae  occur  in  the  hot  springs  of 
Ischia  at  174°  F.  to  185°  F.  Hoppe  Seyler7  found  similar  vegetation 
in  the  hot  waters  of  Lipari  at  127°  F.  The  writings  of  Kiitzing 
mention  a  number  of  species  from  European  hot  springs,  and  other 
localities  are  given  by  Rubenhart. 8 

The  hot  springs  and  geysers  of  Iceland  have  been  famous  for 
many  centuries,  but  a  careful  examination  of  the  writings  of  the 

1  Flora,  1827.  5  Monographia  Nostochinarum  Italica- 

2  Almanach  de  Carlsbad,  1835-'36.  rum  :  Turin,  1842. 
3Linnaea,  1837.  « Sachs  in  Flora,  1864. 
4Abhandl.    Schles.  Gesell.    Naturvviss.,  7  Pflugers  Archiv,  1875. 

Heft  2, 1862.  8  Flora  Aquge  Dalcis. 


622  FORMATION    OF    HOT    SPRING    DEPOSITS. 

numerous  travelers  who  have  visited  and  described  them  shows 
that  only  three  authors  have  mentioned  the  presence  of  algous  vege- 
tation in  the  hot  waters.  Sir  William  Hooker,1  who  visited  Iceland 
in  1809,  found  confervas  at  the  borders  of  many  of  the  hot  springs, 
where  the  plants  were  exposed  to  the  steam  and  heat  of  the  boiling 
water.  Confervas  limosa  Dillw.  was  found  in  abundance,  forming 
large  dark-green  patches  attached  to  a  coarse  white  clay,  from  which 
it  could  be  easily  peeled  off.  A  brick-red  confervse,  an  Oscillatoria, 
occurred  in  a  similar  way,  forming  large  patches  several  inches 
square.  Confervce,  flavescens  Roth,  and  a  species  allied  to  C.  rivu- 
laris,  were  abundant  in  wator  of  a  very  great  degree  of  heat. 

Baring-Gould,  who  visited  the  geysers  in  1864,  found  a  crimson 
algae  growing  in  the  spray  and  overflow  of  the  spring  Tunguhver.* 
He  collected  specimens,  which  were  examined  by  Rev.  J.  M.  Berk- 
ley, who  referred  them  to  the  genus  Hypheothrix,  common  in  hot 
waters  all  over  the  world.  Lauder  Lindsay  found  two  kinds  of  con- 
fervas in  the  springs  of  Laugarnes,  Iceland,  in  water  so  hot  that  an 
egg  was  boiled  in  it  in  four  to  five  minutes. 3 

In  New  Zealand  the  presence  of  algae  in  the  hot  springs'on  the 
south  shore  of  Lake  Taupo  was  first  noted  by  Hochstetter,  who 
says 4  the  dark  emerald-green  growth  covered  the  ground  where  the 
warm  water  flowed.  The  specimens  collected  by  him  are  described 
in  the  Botany  of  the  Novara  Expedition. 

Algse  from  these  springs  are  also  described  by  W.  I.  Spenser,* 
the  highest  temperature  of  the  water  in  which  they  were  found  be- 
ing 136°  F.  Hochstetter  says  the  temperature  of  the  springs  varies 
between  125°  F.  and  153°  F. 

Dr.  S.  Berggren,  of  Lund,  Sweden,  visited  the  hot  spring  district 
of  New  Zealand  in  1874,  and  collected  an  extensive  series  of  speci- 
mens of  the  algae  of  the  region.  He  states6  that  the  algaa,  espe- 
cially Phycochromacece,  but  likewise  Confervacece  and  Zygnem- 
acece,  are  to  be  found  growing  in  great  abundance  in  the  .rivulets 
from  the  hot  springs. 

These  specimens  have  been  studied  by  Dr.  Otto  Nordstedt,  whose 
determinations  show  that  the  species  are  chiefly  those  common  in 
hot  waters  in  other  parts  of  the  world,  and  that  several  species  occur 
both  in  hot  and  cold  waters. 

Thick  masses  of  slimy  confer  void  plants  line  the  bottom  of  a  large 
pool,  Tapui  Te  Koutu,  at  Rotorua,  New  Zealand,  where  the  usual 
temperature  is  90°  to  100°  F.,  but  is  180°  with  a  north  or  east  wind.7 

'Journal  of  a  Tour  in  Iceland,  vol.  1,  p.  160. 

8  Iceland  :  Its  Scenes  and  Sagas. 

3Bot.  Zeitung,  1861,  p.  859. 

4Reise  der  Oe.  Fregatta  Novara  :  Geol.,  vol.  1,  pt.  1,  p.  126. 

5  Trans.  New  Zealand  Inst,  vol.  15,  p.  302. 

6  Kongl.  Sv.  Vet.  Akademiens  Handlingar,  Band  22,  no.  8,  p.  5. 

1  Skey .    Mineral  Waters  of  New  Zealand  •  Trans.  New  Zealand  Inst. ,  vol.  10,  p.  433. 


WEED.]  VEGETATION    OF    HOT    WATERS.  623 

At  the  Azores,  Mr.  Mosely,  naturalist  on  the  Challenger  expedi- 
tion, found  algae  growing  about  the  hot  springs  of  Furnas  Lake, 
island  of  St.  Michael.1  The  algae  occur  on  areas  splashed  by  the 
hot  sulphurous  waters,  forming  a  pale,  yellowish-green  layer  an  inch 
and  a  half  thick.  The  color  is  most  intense  in  the  inner  layers  of 
the  growth.  This  gelatinous  vegetable  matter  occurs  mingled  with 
a  gray  earthy  material  in  successive  layers.  The  temperature  of  the 
water  was  176°  F.  to  194°  F.  A  thick  brilliant  green  deposit,  con- 
sisting of  Chroococcus,  was  found  at  the  edge  of  a  shallow  pool  of 
hot  water  whose  temperature  was  between  149°  F.  and  156°  F.  Speci- 
mens were  also  collected  from  a  swamp  of  hot  mud  in  which,  beside 
algse,  a  rush  (Juncus)  was  found  growing.  The  temperatures  given 
by  Mr.  Mosely  are  all  estimated,  but  are  probably  correct  within  the 
limits  stated.  The  specimens  obtained  from  these  springs  were  ex- 
amined by  Mr.  W.  Archer,  and  the  result  of  his  study  published  in 
a  paper a  which  is  mainly  botanical,  but  is  interesting  in  this  con- 
nection as  showing  the  identity  of  many  of  the  species  from  the 
hot  waters  of  the  Azores,  with  species  common  in  the  cold  waters  of 
Great  Britain. 

In  the  narrative  of  the  voyage  of  the  Challenger,  Mr.  Mosely  de- 
scribes the  occurrence  of  similar  hot- water  growths,  at  the  Banda 
Islands  and  at  the  new  volcano  of  Camiguin.  At  the  first  locality 
gelatinous  masses  of  algae  resembling  those  growing  in  the  Azores 
hot  springs  were  found  around  the  mouths  of  fissures  from  which 
jets  of  steam  issued,  the  only  water  present  being  that  supplied  by 
the  condensation  of  the  vapor.  This  sulphurous  steam  had  a  tem- 
perature of  250°  F.  within  the  fissure,  and  the  thermometer  stood  at 
140°  where  the  algae  flourished.  In  some  places  the  algse  and  a  white 
mineral  incrustation  formed  alternating  layers. 3 

At  the  base  of  the  new  volcano  of  Camiguin  two  hot  streams  were 
full  of  algae.  No  vegetation  was  found  in  hot  water  where  the  tem- 
perature exceeded  145°. 2  F.,  but  in  the  stream-bed  green  patches  oc- 
curred on  stones  projecting  above  the  surface.  As  the  water  of  this 
stream  became  cooler,  a  few  yards  farther  down,  algae  were  found 
growing  in  the  middle  of  the  channel  at  113°. 5  F.  ''This,"  says  Mr. 
Mosely,  "seems  to  be  the  limiting  temperature  for  this  particular 
algae  in  this  water."  Where  the  temperature  of  the  stream  was  122° 
F.  it  fed  a  little  side  pool  where  algae  were  growing  at  a  temperature 
of  101°.5  F.4 

Dr.  Hooker  found  a'gae  in  the  hot  springs  of  the  Himalayas  at 
several  localities. '  At  Soorujkoond  or  Belcuppec  (in  the  Behar  Hills) 

1  Journ.  Linn.  Soc.  (Bot.),  vol.  14,  1875,  p.  321. 
2 Ibid.,  p.  328. 

3  Voyage  of  H.  M.  S.  Challenger:  Narr.,  vol.  1,  part  I,  p.  563. 

4  Ibid,  p.  654. 


624  FORMATION    OF    HOT    SPRING    DEPOSITS. 

brown  and  green  algae  were  found  forming  broad,  luxuriant  strata 
where  the  temperature  did  not  exceed  168°  F.,  the  growth  thriving 
until  the  water  had  cooled  down  to  90°  F,  The  brown  algse  were 
found  in  deeper  and  hotter  water  than  the  green.  In  an  appendix, 
Rev.  J.  M.  Berkley,  writing  about  the  specimens  collected  from  these 
springs,  says  a  Leptothrix  occurs  from  80°  F.  to  158°  F.,  an  imperfect 
Zygnema  between  84°  F.  and  112°  F.2  The  same  writer  also  describes 
specimens  collected  by  Dr.  Hooker  from  the  hot  springs  of  Momay 
at  110°  F.,  and  from  Pugha,  Thibet,  in  springs  having  a  temperature 
of  174°  F.3 

Green  algous  growths  were  observed  by  Prof.  J.  D.  Dana  in  the 
hot  springs  of  Luzon  at  160°  F.,4  and  similar  vegetation  was  found 
in  the  Celebes  hot  springs  in  waters  of  123°.  8  F.  and  170°  F.  by  Prof. 
A.  S.  Bickmore.6  Green  algous  vegetation  was  also  noted  in  many 
Japanese  hot  springs  by  Benj.  Smith  Lyman.8  Cushion-shaped 
masses  of  slippery  gelatinous  vegetation — Oscillatoria  labyrinthi- 
formis  Ach. — were  found  by  Junghuhn  in  the  hot  springs  of  Java 7  at 
150°  F.,  and  a  species  of  Oscillaria  was  found  associated  with  a  milk 
white  precipitate  of  sulphate  of  lime  at  Tji-Panas. 

In  the  United  States  algse  have  been  found  in  hot  springs  at  many 
localities.  Red,  white,  and  green  growths  occurring  in  the  warm 
sulphur  springs  of  Virginia  have  given  rise  to  the  names  of  many  of 
these  famous  resorts. 8  At  the  hot  springs  of  Arkansas  green  cryp- 
togamic  vegetation  occurs  in  water  having  a  temperature  of  140°  F. , 
and  a  species  from  this  place  is  described  by  Kutzing.9 

At  the  so-called  "  geysers"  of  Pluton  Creek,  California,  green  algse 
occur  in  the  hot  acid  water  in  great  abundance.  Prof.  W.  H. 
Brewer  found  that  the  highest  temperature  noted  at  which  the  plants 
were  growing  was  200°  F.,  but  they  were  most  abundant  in  waters 
of  125°  F.  to  140°  F.  The  growth  in  the  hottest  waters  was  appar- 
ently of  the  simplest  kind,  and  composed  of  simple  bright-green  cells. 
Where  the  water  had  cooled  to  140°  F.  to  149°  F.,  bright-green  fila- 
mentous confervas  formed  in  considerable  masses.  Similar  growths 
formed  coatings  on  the  soil  about  steam- jets,  and  were  alternately 
exposed  to  very  hot  steam  and  cooler  air.  In  a  specimen  collected 
from  water  having  a  temperature  of  130°  F. ,  Mr.  A.  M.  Edwards,  of 

1  Himalayan  Travels  :  Jos.  Dalton  Hooker,  vol.  1,  pp.  27,  379. 

2  The  temperatures  given  by  Mr.  Berkley  are  10°  lower  than  those  given  by 
Hooker. 

3Loc.  cit.,  p.  379. 

1  Manual  of  Geology,  by  Jas.  D.  Dana:  3d  ed.,  1880,  p.  612. 

5  Travels  in  East  Indian  Archipelago. 

"Prelim.  Reports,  Geol.  Surv.,  Japan,  1874,  1877,  1879. 

7  Java,  Seine  Gestalt,  Fr.  Junghuhn :  vol.  2,  pp.  864,  866,  868,  870,  873. 

8  Geology  of  the  Virginias,  W.  B.  Rogers,  pp.  107,  589. 
'  Species  Algarum. 


WEED.]  VEGETATION    OF    HOT    WATERS.  625 

New  York,  is  said  to  have  found  animal  as  well  as  vegetable  organ- 
isms. Professor  Brewer  also  states  that  in  the  hot  siliceous  waters 
of  Steam-boat  Springs,  Nevada,  there  is  an  abundant  confervoid 
vegetation  in  the  gelatinous  mass  formed  where  the  water  spreads 
out  over  the  surface.  This  was  most  plentiful  where  the  tempera- 
ture was  about  100°  F.  The  most  interesting  feature  of  this  occur- 
rence is  the  abundant  vegetation  in  the  gelatinous  silica.5  Mr. 
James  Blake  found  diatoms  in  water  having  a  temperature  of  163° 
F.  at  the  Pueblo  Hot  Springs,  Nevada.*  The  algae  growing  in  the 
Benton  Spring,  Owen's  Valley,  California,  are  described  by  Mrs.  Partz 
as  representing  three  forms.  The  first  is  developed  in  the  basin  of  the 
spring  at  a  temperature  of  124°  F.  to  135°  F.,  the  temperature  of  the 
water  at  the  point  of  issue  being  160°  F.  In  the  warm  creek  formed 
by  the  overflow  of  the  spring  the  algse  form  waving  fibers  two  feet 
long,  at  temperatures  between  110°  F.  and  120°  F.  Below  100°  F. 
these  plants  cease  to  grow,  but  a  bright-green,  slimy  fungus  occurs, 
disappearing  as  the  temperature  decreases.  Dr.  H.  C.  Wood  gives 
technical  descriptions  of  these  plants,3  and  says  the  forms  develope 
at  the  highest  temperatures  are  immature.  The  presence  of  green 
confervoid  vegetation  in  many  other  hot  springs  has  been  noted  by 
various  writers,  but  no  description  has  been  given  either  of  the 
plants  themselves  or  of  the  temperature  and  other  conditions  gov-  , 
erning  their  occurrence. 

In  the  hot  springs  of  the  Yellowstone  National  Park  no  plant  life 
has  been  found  at  a  temperature  exceeding  185°  F.,  but  at  tempera- 
tures between  90°  F.  and  185°  F.  algous  growtlis  are  generally  pres- 
ent. In  the  reports  of  the  Hayden  Survey  for  1871  and  1872  there 
are  several  references  to  the  presence  of  vegetation  in  the  hot  waters. 
At  the  Mammoth  Hot  Springs,  Dr.  F.  V.  Hayden  observed  the 
occurrence  of  pale  yellow  filaments  about  the  springs  and  the  green 
•confervoid  vegetation  of  the  waters,  as  well  as  the  presence  of  di- 
atoms in  the  basins  of  the  main  springs,  two  species  of  the  latter, 
Palmella  and  Oscillaria,  being  recognized  by  D.  Billings.4  Green 
vegetation  was  also  noted  in  the  hot  waters  of  the  Washburne,  Peli- 
can, and  Terrace  Springs,  and  at  the  Lower  Geyser  Basin.5  The 
brown  leathery  lining  of  the  springs  of  the  Lower  Geyser  Basin  of 
the  Firehole  River  was  thought  by  Dr.  Hayden  to  be  an  aggrega- 
tion of  diatoms  covered  with  iron  oxide.6  In  1872  Prof.  F.  H. 
Bradley  recognized  the  presence  of  vegetation  in  the  hot  springs  of 
the  park,  and  writing  of  the  hot  waters  of  the  Geyser  Basins,  says 

1  Amer.  Jour.  Sci.,  2d  series,  vol.  41,  p.  391. 

1  Manual  of  Geology,  by  James  D.  Dana,  3d  ed.,  1880,  p.  611. 

3 Amer.  Jour.  Sci.,  2d  series,  vol.  46,  p.  31. 

4  Ann.  Kept.  U.  S.  Geol.  and  Geogr.  Survey  of  the  Territories  for  1871,  pp.  69,70. 

5Loc.  cit.,  p.  136,  and  1872  report,  p.  55. 

«Loc.  cit,  1871,  p.  105. 

9  GEOL 40 


626  FORMATION    OF   HOT    SPRING    DEPOSITS. 

that  there  are  gelatinous  forms  allied  to  mycelium,  or  mother  of 
vinegar,  in  nearly  all  the  pools,  except  where  the  ebullition  is  so 
strong  as  to  break  up  such  tender  tissues.  This  material  occurred  in 
broad,  thick  sheets  of  green  or  rusty  brown,  in  thick,  branching 
forms,  resembling  sponges,  or  in  long  waving  white  fibers. '  In  the 
mucilaginous  deposit  on  the  side  of  a  spring  at  the  Lower  Geyser 
Basin  Dr.  Josiah  Curtis  found  skeletons  of  diatoms,  but  no  living 
ones.  Professor  Bradley  said  the  colors  striping  the  mound  of  the 
Solitary  (Lone  Star)  Geyser  are  due  to  purely  vegetable  material. 
His  assistant,  Mr.  Taggart,  reported  leafy  vegetation  in  springs  of 
120°  or  less  at  Lewis  Lake,  where  the  springs  of  higher  temperature 
contained  pulpy  masses  of  a  fungoid  growth  common  about  the  hot 
springs  of  the  Geyser  Basins.2  The  botanist  of  the  expedition, 
Prof.  John  Coulter,  says  in  his  report  that  algae  were  discovered 
growing  in  some  of  the  hot  springs.  He  collected  orange-colored 
confervoid  specimens  from  the  waters  of  the  Lower  Geyser  Basin 
which  were  identified  by  Charles  H.  Peck  as  Confervas  atirantfca.9 
Prof.  Theodore  Comstock,  who  visited  the  park  with  the  Jones  ex. 
pedition  in  1873,  records  the  presence  of  green  confervse  in  the  Green 
Spring.  Pelican  Creek,  at  104°  F. ,  and  similar  growths  were  found 
at  Turbid  Lake,  Mammoth  Hot  Springs,  Excelsior  Geyser,  Sapphire 
Springs,  and  the  Lake  Shore  Hot  Springs.4  The  same  observer 
noticed  the  silken  yellow  filaments  at  the  Mammoth  Hot  Springs, 
and  supposed  the  abundant  "colloid  matter"  of  the  springs  to 
originate  from  organic  matter  contained  in  the  water,  the  forms 
being  produced  by  the  rising  or  buoyancy  of  bubbles  of  carbonic 
acid  gas. 5  Dr.  C.  C.  Parry,  botanist  of  this  expedition,  noticed  the 
presence  of  algse  in  the  hot  springs  of  the  park,  and  says  they  will 
reward  special  research.6 

The  report  of  Dr.  A.  C.  Peale  upon  the  thermal  springs  of  the 
Yellowstone  National  Park 7  contains  but  little  about  the  vegetation 
of  the  Park  hot  springs.  Under  the  heading,  "  Life  in  Hot  Springs,'* 
he  says : 

At  numerous  places  in  all  the  geyser  areas  and  at  Gardiner's  River  masses  of 
gelatinous  material  of  greenish -red,  yellow,  and  brown  colors  are  noticed,  and  usu- 
ally have  been  considered  of  organic  origin.  In  most  cases  where  microscopical 
examination  has  been  made  no  trace  of  vegetable  organization  has  been  noted,  and 
in  regions  where  the  springs  are  siliceous  this  curious  material  is  probably  that  form 
of  gelatinous  silica  described  in  another  place  as  viandite.  In  some  springs  of  very 
low  temperature  a  brown,  leathery-looking  material  is  found  lining  the  basins.  It 

'Ann.  Kept.  U.  S.  Geol.  and  Geog.  Survey  of  the  Territories  for  1872,  pp.  207,  231. 
2Loc.  cit.,  1872,  p.  250. 
3Loc.  cit.,  p.  752. 

4  Report  of  Reconn.  N.'W.  Wyoming  in  1873,  by  Capt.  Wm.  Jones,  U.  S.  War 
Dept.,  pp.  190,  194,  210,  228,  231,  238. 
6Loc.  cit,  p.  207. 
6  Amer.  Naturalist,  1874,  p.  178. 
'Final  Rept.  U.  S.  Geol.  and  Geog.  Survey  Terr.,  1878,  vol.  2,  p.  359. 


WEED.]  VEGETATION    OF    HOT    WATEKS.  627 

becomes  hard  upon  drying,  but  has  not  as  yet  been  examined  microscopically  or 
chemically,  so  that  its  nature  is  unknown,  but  in  all  probability  it  is  one  of  the 
forms  of  silica  rather  than  an  organic  material. 

This  evidently  represents  the  views  of  Dr.  Peale  and  his  colleagues 
regarding  the  nature  of  the  algous  growths  of  the  Park  hot  springs 
at  the  time  this  report  was  prepared. 

This  review  of  the  literature  of  the  subject  shows  how  few  occur- 
rences of  hot-spring  vegetation  have  as  yet  been  carefully  observed 
and  described.  In  the  cases  noted,  naturalists  have  generally  given 
the  temperature  of  the  water  in  which  the  plants  were  found,  and 
the  specimens  collected  have  been  studied  from  a  purely  botanical 
point  of  view,  but  with  the  notable  exception  of  Prof.  Ferd.  Cohn, 
observers  have  entirely  overlooked  the  geological  work  of  the  lowly 
organized  plants  and  the  part  they  take  in  the  production  of  hot- 
spring  deposits. 

Thtse  hot-water  growths,  like  all  fresh-water  algae,  are  more 
widely  distributed  than  any  other  plants  save  those  peculiar  to 
brackish  waters.  This  is  shown  by  the  occurrence  of  algous  vegeta- 
tion in  the  hot  springs  of  such  widely  separated  localities  as  Iceland, 
the  Azores,  New  Zealand,  Japan,  and  the  United  States.  A  com- 
parison of  the  species  shows  that  the  flora  is  very  uniform  in  char- 
acter, being  limited  to  a  few  groups  and  the  species  themselves  being 
identical  to  a  great  extent. 

Perhaps  the  most  interesting  feature  connected  with  the  life  of 
these  algae  is  their  tolerance  of  a  high  degree  of  heat.  The  extreme 
temperature  at  which  vegetation  has  been  observed  is  200°  F.,  re- 
corded by  Prof.  W.  H.  Brewer  at  the  California  "Geysers."  On 
the  island  of  Ischia,  near  Naples,  no  algse  were  found  in  hot  waters 
above  185°  F.,  which  accords  with  the  observations  made  in  the  Yel- 
lowstone National  Park.  At  other  places  these  growths  have  not 
been  found  at  such  high  temperatures.  Dr.  J.  D.  Hooker  found  the 
limit  to  be  168°  F.  in  the  Himalayan  springs,  and  Prof.  Ferd.  Cohn 
says  no  growths  are  present  in  the  Carlsbad  waters,  where  the  tem- 
perature exceeds  44°  R.  (131°  F.).  As  regards  the  effect  of  the 
chemical  substances  dissolved  in  the  water  there  is  but  little  known, 
but  vegetation  has  been  found  in  all  varieties  of  water,  sulphurous, 
calcareous,  acid,  and  alkaline,  and  so  far  as  observed  the  amount  of 
material  held  in  solution  does  not  affect  the  growth.  Certain  species, 
however,  are  known  to  be  peculiar  to  particular  waters.  Thus  the 
Beggiatoce,  form  the  characteristic  vegetation  of  sulphur  springs, 
and  Gaillionce,  are  found  in  iron-bearing  waters.  The  adapta- 
bility of  particular  algae  to  extreme  conditions  of  environment  is 
shown  by  the  occurrence  of  the  same  species  in  the  highly  heated 
sulphurous-siliceous  waters  of  the  Azores  and  the  cold  surface  waters 
of  Great  Britain. 

Altitude  is  not  known  to  affect  the  growths,  and  algee  are  found 


628  FORMATION    OF    HOT    SPRING    DEPOSITS. 

in  Iceland  but  a  few  hundred  feet  above  sea  level,  in  the  Yellow- 
stone National  Park  at  7,500  feet,  and  in  the  Himalayas  at  an  eleva- 
tion of  17,000  feet. 

HOT  SPRINGS  OF  THE  YELLOWSTONE  NATIONAL  PARK. 

Regions  of  solfataric  activity  have  always  been  of  peculiar  inter- 
est to  scientific  observers,  not  only  on  account  of  the  curious  and  often 
extremely  beautiful  hot  springs  and  the  rarer  occurrence  of  geysers 
in  such  districts,  but  also  from  the  varied  phenomena  of  rock  decom- 
position and  of  mineral  formation  and  deposition  which  always 
accompany  such  hydrothermal  action.  It  is  in  these  natural  labora- 
tories that  we  are  permitted  to  see  in  operation  processes  which  have 
produced  important  changes  in  the  rocks  of  the  earth's  crust  and 
afford  a  key  to  many  of  the  problems  of  chemical  geology. 

There  is  perhaps  no  other  district  in  the  world  where  hydrother- 
mal action  is  as  prominent  or  as  extensive  as  it  is  in  the  Yellowstone 
National  Park.  In  this  area  of  about  3, 500  square  miles,  over  3, 600 
hot  springs  and  100  geysers  have  been  visited  and  their  features* 
noted,  and  there  are  also  almost  innumerable  steam  vents.  With  few 
exceptions  the  hot  waters  are  siliceous,  and  rise  through  the  acidic 
lavas  of  the  park,  and  it  is  probable  that  it  is  owing  to  this  fact  that 
the  deposits  formed  by  the  hot  waters  do  not  differ  more  in  charac- 
ter. The  facts  upon  which  this  paper  is  based  have  been  obtained 
in  the  course  of  a  series  of  comparative  observations  carried  on  by 
the  writer  for  the  past  six  years  at  the  different  hot-spring  areas  of 
the  Park,  under  the  direction  of  Mr.  Arnold  Hague,  geologist  in 
charge  of  the  Geological  Survey  of  the  Yellowstone  National  Park. 

THE  MAMMOTH  HOT  SPRINGS. 

Although  the  Yellowstone  Park  abounds  in  hot  springs,  calcareous 
hot  waters  are  extremely  rare,  and  but  one  locality  is  known  where 
such  springs  have  formed  deposits  of  travertine,  or  calcareous  tufa, 
of  any  considerable  extent.  This  is  the  Mammoth  Hot  Springs.  At 
this  place  the  heated  waters  rising  through  Mesozoic  limestone  reach 
the  surface  heavily  charged  with  carbonate  of  lime  in  solution,  which 
is  deposited  by  the  hot  waters  in  the  form  of  travertine,  affording  an 
excellent  opportunity  for  a  study  of  the  formation  of  this  mineral. 

Calcareous  hot  waters  are  not  rare  in  nature,  but  are  found  in 
many  parts  of  the  world,  and  are  usually  surrounded  by  deposits 
of  travertine  often  of  considerable  extent  $  yet  there  are  few  places 
where  such  deposits  equal  those  of  the  Mammoth  Hot  Springs  in  mag- 
nitude, and  none  exceeding  them  in  beauty.  The  travertine  deposits 
of  Hierapolis  in  Asia  Minor,  famous  for  its  hot  waters  in  the  time 
of  the  Emperor  Coiistantine,  form  a  white  hill  whose  slopes  are  orna- 
mented with  basins  resembling  those  of  the  Marble  Terrace  of  the 
Mammoth  Hot  Springs,  and  the  springs  of  the  Hammon  Meschoutin, 


WEED.]  TRAVERTINE    DEPOSITS.  629 

in  Algeria,  have  built  up  cones  and  ridges  which  are  the  duplicate 
of  those  found  on  the  terraces  of  our  own  locality. 

GEOLOGICAL  RELATIONS. 

The  Mammoth  Hot  Springs  form  the  most  northern  of  the  numer- 
ous hot-spring  areas  of  the  Park,  being  situated  in  the  northwest 
corner  of  the  reservation,  three-quarters  of  a  mile  south  of  the  forty- 
fifth  parallel,  which  forms  the  Montana- Wyoming  boundary.  As  it 
is  but  seven  miles  from  the  terminus  of  the  railroad  it  forms  the  first 
stopping  place  of  the  traveler  who  enters  the  Park  from  the  north, 
and  it  is  the  most  accessible  of  the  many  points  of  interest  in  this 
region.  The  situation  is  extremely  picturesque ;  the  dark  and  lofty 
summit  of  Sepulchre  Mountain  rising  near  by  on  the  north,  while  the 
upper  valley  of  the  Yellowstone  and  the  sharp  peaks  of  the  Snowy 
Range  are  seen  at  the  northeast,  between  the  slopes  of  Sepulchre 
and  the  long  mural  face  of  Mount  Evarts.  In  the  southeast  the  eye 
dwells  pleasingly  upon  the  distant  view  of  the  ravine  of  Lava  Creek 
and  Undine  Falls,  with  many  snow-flecked  peaks  in  the  far  distance. 
Bunsen  Peak  rises  abruptly  in  the  south,  its  dark  slopes  forming  a 
pleasing  background  to  the  white  mass  of  hot-spring  deposit  when 
seen  from  the  north.  This  deposit  fills  an  ancient  ravine  lying  be- 
tween Terrace  Mountain  and  Sentinel  Butte,  the  grassy  slopes  of  the 
latter  showing  exposures  of  Jurassic  and  Cretaceous  limestones 
carved  into  well-defined  benches  by  glacial  action.  Immediately 
south  of  the  travertine  terraces  the  sedimentary  strata  are  covered 
by  rhyolite,  the  northern  extension  of  the  great  lava  flows  which  fill 
the  ancient  basin  of  the  Park.  Near  the  Gardiner  River,  Cretaceous 
sandstones  form  small  ridges,  dividing  the  travertine  sheet  into 
three  tongues ;  these  beds  dip  steeply  eastward,  passing  beneath  the 
strata,  forming  the  face  of  Mount  Evarts. 

TRAVERTINE  DEPOSITS. 

The  total  area  covered  by  the  travertine  is  about  two  square  miles, 
including  the  beds  of  preglacial  age  which  form  the  summit  of  Ter- 
race Mountain.  The  greatest  thickness  is  probably  about  two  hun- 
dred and  fifty  feet,  but  the  average  is  very  much  less.  The  upper 
limit  of  the  deposit,  forming  the  terraces  and  filling  the  ravine,  is 
about  1,400  feet  above  the  Gardiner  River  and  7,100  feet  above  sea 
level ;  the  travertine  extends  from  this  terrace  down  to  the  river, 
forming  a  continuous  covering  of  varying  width  and  thickness.  It 
is  impossible  to  measure  the  volume  of  the  deposit  as  the  thickness 
is  variable,  and  the  contour  of  the  underlying  surface  can  be  con- 
jectured only  by  the  relation  of  the  neighboring  slopes. 

The  usual  approach  to  the  Mammoth  Hot  Springs  from  the  rail- 
road is  over  the  road  leading  up  the  picturesque  gorge  of  the  Gar- 
diner to  the  foot  of  the  terraces.  Recrossing  this  stream  near  its 


630  FORMATION    OF    HOT    SPRING    DEPOSITS. 

junction  with  the  Hot  River,  the  road  gradually  ascends  to  the  flat 
or  terrace  on  which  the  hotels  stand,  500  feet  above  the  river.  The 
road  is  built  upon  the  hot-spring  deposit,  hidden  on  the  lower  slopes 
by  drift  and  soil  but  exposed  during  the  last  200  feet  of  the  ascent, 
where  many  well-preserved  basins  may  be  seen  on  the  pine  and 
cedar  covered  slopes. 

When  first  seen  the  main  mass  of  the  recent  deposit  is  striking 
from  its  whiteness,  resembling  an  immense  snow-bank,  filling  a  nar- 
row valley  whose  pine-clad  sides  are  in  strong  contrast  to  the  white 
travertine.  It  has  been  compared  by  Prof.  Arch.  Geikie  to  the  ter- 
minal front  of  a  glacier,  and  by  other  writers  to  a  foaming  cascade 
suddenly  turned  into  stone.  Streaks  and  patches  of  red,  yellow, 
and  green  seen  upon  these  white  slopes  mark  the  course  of  the  over- 
flowing waters,  and  clouds  of  steam  float  lightly  upward  from  the 
springs  of  the  main  terrace  and  vanish  in  mid-air.  There  are  in  all 
eight  well-defined  benches  or  terraces  formed  by  the  travertine,  each 
with  a  more  or  less  level  surface,  and  terminated  by  steep  slopes 
leading  to  the  terrace  below.  The  largest  of  these  flats  is  the  Hot£l. 
terrace,  which  is  83  acres  in  extent.  This  possesses  several  features 
of  interest.  These  are  usually  overlooked  in  the  desire  to  see  the 
greater  wonders  and  beauties  of  the  upper  terraces,  but  one  can 
scarcely  fail  to  notice  the  Liberty  Cap,  a  pillar  43  feet  in  height 
with  sphinx-like  profile,  the  cone  of  a  hot  spring  long  extinct.  This 
cone  and  its  companion,  the  Thumb,  with  the  immense  empty  hot- 
spring  bowls  of  this  terrace,  attest  an  activity  and  size  for  these 
extinct  springs  far  surpassing  any  now  active. 

THE   SPRINGS   AND   THEl^l    VEGETATION. 

With  the  exception  of  the  Hot  River  all  the  active  springs  now 
issue  from  the  terraces  above  the  hotels,  or  from  the  upper  part  of 
the  hotel  terrace  itself.  These  seventy-five  springs  vary  in  tempera- 
ture from  80°  F.  up  to  165°  F.,  and  in  size  from  small  oozes  of  hot 
water  to  basins  50  by  100  feet  across,  with  an  overflow  of  many  thou- 
sand gallons  per  hour.  Algae  have  been  found  in  all  these  springs, 
and  it  is  this  vegetation,  and  the  part  which  it  takes  in  the  forma- 
tion of  travertine  by  the  hot  waters,  that  are  of  especial  interest  in 
the  present  paper. 

In  wandering  around  the  terraces  of  this  great  deposit  of  traver- 
tine the  observer  is  sure  to  be  impressed  with  the  brightly  tinted 
basins  about  the  springs  and  the  red  and  orange  colors  of  the  slopes 
overflowed  by  the  hot  waters.  These  colors  are  due  to  the  presence 
of  microscopic  algae,  which  are  not  easily  recognizable  in  this  deposit, 
owing  to  their  covering  of  travertine.  In  the  cooler  springs  and 
channels  similar  vegetation  forms  the  bright  green,  orange,  or 
brown  membrane-like  sheets  or  masses  of  jelly,  without  apparent 
vegetable  structure. 


WEED.]  'GENERAL    OCCURRENCE    OF    THE    ALG.E.  631 

The  true  nature  of  the  silken  yellow  filaments  found  in  the  bowls 
and  channels  of  even  the  hottest  springs  is  more  apparent,  though 
the  yellow  color  is  due  to  sulphur  incrusting  the  algae  threads.  The 
intimate  relation  of  these  algous  growths  to  the  deposits  of  newly 
formed  travertine  suggests  at  once  that  the  algae  are  encrusted  by 
the  carbonate  of  lime,  and  so  aid  in  the  formation  of  the  tufa. 
While  this  is  probably  true,  the  chief  work  of  these  plants  is  the 
separation  from  the  water  of  the  carbonate  of  lime,  which  they 
cause  by  their  abstraction  of  carbonic  acid.  Owing  to  this  action,  a 
common  function  of  vegetation,  such  growths  are  an  important 
factor  in  the  formation  of  travertine  by  the  Mammoth  Hot  Springs 
waters. 

GENERAL  OCCURRENCE  OF  THE  ALGJE. 

The  general  occurrence  of  the  algous  vegetation  will  be  best  un- 
derstood if  a  brief  description  of  a  few  of  the  typical  springs  is 
given. 

The  largest  springs  now  active  are  those  of  the  Main  Terrace. 
This  is  a  fairly  flat  area  of  8f  acres  in  extent  and  250  feet  above  the 
hotels.  On  the  north  the  terrace  ends  in  abrupt  slopes,  extending 
down  to  the  bench  below ;  on  the  east  and  so'utheast  the  descent  is 
more  gradual,  extending  down  to  the  military  quarters  175  feet  be- 
low. Near  the  center  of  this  terrace  are  the  Blue  Springs.  These 
springs  shift  their  position  from  year  to  year,  the  rapid  deposition 
of  travertine  choking  up  the  vents,  causing  the  springs  to  seek  other 
and  easier  outlets.  In  this  case  it  often  happens  that  the  pressure 
of  the  accumulated  gas  fractures  the  deposit,  and  the  water  issues  in 
a  jet  a  foot  or  more  in  height.  A  rim  of  travertine  is  soon  built  up 
about  the  vent,  forming  a  basin,  into  which  the  water,  no  w^  relieved 
of  the  excess  of  pressure,  issues  quietly,  though  in  considerable  vol- 
ume. The  most  beautiful  of  the  Blue  Springs  is  a  pool  15  by  20  feet 
in  extreme  dimensions  filled  with  pellucid  water  apparently  in  vio- 
lent ebullition.  The  sides  and  bottom  of  the  basin  are  formed  of 
pure  white  travertine,  while  the  varying  depths  cause  the  water  to 
appear  all  shades  of  blue  and  green,  from  a  deep  peacock  blue  in 
the  deeper  parts  of  the  bowl  to  the  lightest  of  Nile  greens  in  the 
shallower  recesses.  The  water,  issuing  with  a  temperature  of  165° 
F.,  contains  a  large  amount  of  gas,  which  escapes  at  the  surface  of 
the  pool,  causing  the  water  to  rise  in  a  low  dome,  variations  in  the 
amount  of  gas  producing  a  pulsating  movement,  sending  out  waves 
which  ripple  across  the  water  and  curl  over  the  shallow  margin  of 
the  bowl.  The  overflow  passes  over  and  under  large  fan-shaped 
masses  of  fibrous  white  or  yellow  travertine  (Fig.  52)  into  the  upper- 
most of  a  series  of  basins  irregularly  arranged  in  tiers,  a  portion 
running  in  serpentine  waterways  built  up  of  travertine.  These 
natural  aqueducts  are  often  two  or  three  feet  high.  In  the  center  is  a 


632  FORMATION    OF    HOT    SPRING    DEPOSITS. 

shallow  gutter  too  small  to  hold  the  volume  of  the  stream,  whicK 
overflows  the  sides  and  fills  the  basins  along  its  course. 


FIG.  52.  Travertine  fan,  main  terrace,  Mammoth  Hot  Springs. 

These  terraced  overflow  basins  form  the  most  striking  feature  of 
the  springs.  No  description  can  do  justice  to  their  beauty,  for 
neither  the  delicate  fretwork  of  their  walls  nor  the  frosted  surface 
of  the  glistening  deposit,  nor  the  brilliant  colors  of  the  pools  and  rims 
can  be  described.  Plate  LXXVIII,  from  a  photograph,  shows  a  few 
of  the  many  basins,  of  which  each  differs  from  the  others.  The  walls 
are  built  up  of  pure  white  travertine,  the  surface  resembling  imbri- 
cated shells  or  a  multitude  of  miniature  basins,  and  often  covered 
with  a  brightly  colored  vegetable  jelly,  where  the  water  is  slightly 
cooled.  These  basin  walls  vary  in  height  from  a  few  inches  to  sev- 
eral feet.  Their  outline  is  rarely  crescentic,  usually  irregular,  wavy, 
and  scalloped.  The  water  runs  over  the  rims  in  thin  sheets  and 
little  cascades,  depositing  travertine  wherever  it  flows  and  constantly 
building  up  the  basins  until  the  flow  is  checked  by  the  increased 
height  of  the  rims.  Yellow  sulphur-coated  algse  threads  are  abun- 
dant in  the  bowl  of  the  spring  and  the  rapid-flowing  streams,  but 
the  exquisite  blues  and  greens  of  the  hottest  basins  are  due  solely  to 
the  varying  depths  of  water.  The  bright  lemon,  red,  arid  green 
shades  of  the  cooler  pools  are,  however,  entirely  vegetable  in  their 
nature,  and  due  to  the  presence  of  algse  lining  the  basins  and  strip- 
ing their  outer  walls.  In  a  general  view  of  the  entire  collection  of 
these  basins,  obtained  from  the  edge  of  the  terrace  above,  the  effect 
is  that  of  a  brilliant  mosaic,  the  colors  occurring  in  well-defined 
areas  outlined  by  the  white  travertine  rims.  As  will  be  shown  later, 
the  contrasting  tints  of  adjacent  basins  are  due  to  the  different  tem- 
perature of  the  water  and  consequent  different  development  of  the 
algous  vegetation.  Looking  at  the  pools  near  by  proves  that  these 
colors  are  not  pure,  but  are  produced  by  a  number  of  tints,  minute 
differences  in  depth  producing  variations  in  color  in  the  same  basin. 
Large  as  is  the  overflow  from  the  Blue  Springs,  little  reaches  the 
edge  of  the  terrace,  the  water  sinking  into  the  porous  deposit  or  flow- 
ing into  holes  and  fissures  in  the  travertine  floor. 

On  the  same  terrace,  but  close  to  the  southeastern  edge,  are  the 


WEED.]  EFFECT    OF    ENVIRONMENT.  633 

two  main  springs.  They  are  very  much  alike,  and  are  to-day  in 
nearly  the  same  condition  as  in  1871,  when  they  were  first  seen. 
The  northern  spring  is  a  brown  lined  bowl,  75  by  100  feet  across,  and 
5  to  8  feet  deep.  The  flat  margin  is  formed  of  smooth  and  polished 
salmon-colored  travertine  whose  thin  laminse  and  hardness  show  it 
to  have  been  quite  slowly  formed.  The  water  is  much  cooler  than 
that  of  the  Blue  Springs,  having  a  temperature  of  136°  F.  at  the  edge 
of  the  bowl.  The  supply  is  constant  and  issues  from  holes  in  the 
bottom  of  the  basin,  their  location  being  distinguished  by  the  lighter 
color  of  the  water,  the  eddying  currents,  and  an  occasional  stream 
of  gas  bubbles. 

The  perfect  transparency  of  the  water  enables  one  to  see  the  mi-( 
nutest  details  of  the  sides  and  bottom  of  the  bowl.  The  volume  of 
water  which  the  two  main  springs  pour  out  is  not  known,  as  the  out- 
flow does  not  run  in  definite  channels,  but  pours  over  the  eastern 
margins  in  a  shallow  sheet  which,  spreading  out,  flows  down  the 
rippled  slopes  and  over  the  Marble  Basins.  PI.  LXXIX  shows  a  few 
of  the  upper  basins,  which  are  often  quite  shallow,  and  hardly  merit 
the  name  of  basin.  Here  the  waters  deposit  carbonate  of  lime  rap- 
idly, and  the  walls  or  basin-fronts  are  generally  solid,  while  on  the 
lower  slope  the  cooled  waters  have  parted  with  much  of  their  lime, 
and  deposit  travertine  slowly.  On  these  lower  slopes  the  basins  are 
fringed  with  slender  stalactites  and  pillars,  forming  the  beautiful 
Pulpit  Basins,  illustrated  in  PI.  LXXX.1  In  this  case,  also,  the  pool 
or  basin  proper  is  very  shallow,  rarely  a  foot  deep,  and  the  rim  or 
lip  generally  projects  over  the  pillared  front,  as  it  is  here  that  the 
deposition  of  travertine  is  most  rapid. 

Wherever  the  hot  waters  fl<fw  the  deposit  is  brightly  colored  by 
the  algous  vegetation.  The  pools  and  basins  near  the  springs  are 
lined  with  deep  red,  while  the-  slopes  below  are  bright  orange  in 
color,  and  it  is  only  near  the  base  of  the  slope,  where  the  waters  are 
quite  cool,  that  this  color  disappears. 

EFFECT   OF   ENVIRONMENT. 

Algae  are  abundant  in  all  the  springs  and  wherever  the  hot  waters 
flow,  but  the  growths  vary  in  character  and  in  color  with  the  tem- 
perature of  the  water  and  with  the  situation  in  which  they  occur. 
If  the  temperature  exceeds  150°  F.  a  white  filamentary  algaisjlie 
only  species  present,  the  thread  generally  coated  with  sulphur;  but 
where  the  water  has  cooled  below  that  point,  or  issues  with  a  lower 
temperature,  a  pale  greenish-yellow  growth  is  found,  sparingly  at 
first,  but  more  abundantly  and  deeply  tinted  in  cooler  water,  where 
it  often  entirely  replaces  the  white  species.  This  green  alga  is  asso- 
ciated in  turn  with  a  red  or  orange  species  which  gradually  replaces 

1  Plates  LXXVIII,  LXXIX,  and  LXXX  are  engraved  from  photographs  made  by 
T.  W.  Ingersoll.  of  St.  Paul,  Minn. 


634 


FORMATION    OF    HOT    SPRING    DEPOSITS. 


it  in  the  cooling  waters,  while  in  tepid  streams  too  cool  to  support 
any  of  these  forms  an  olive-brown  species  forms  a  soft,  velvety  cover- 
ing over  the  travertine.  Different  conditions  of  flow  and  current  pro- 
duce varying  forms  of  the  same  growth.  In  a  rapid  current  the  algae 
are  filamentary,  while  in  quieter  water  the  threads  are  united  together 
in  a  membrane-like  sheet  or  in  masses  of  jelly,  generally  inflated  by 
gas  bubbles  entangled  in  the  vegetable  tissue.  At  the  borders  of 
many  channels  the  two  forms  pass  into  each  other.  Where  the  depo- 
sition of  travertine  is  very  rapid,  as  is  generally  the  case  on  the  over- 
flow slopes  and  basin  walls,  the  algae  are  encased  in  the  deposit  and 
only  the  vegetating  ends  of  the  filaments  are  exposed  and  free. 

The  white  algae,  which  grow  in  the  hotter  waters,  are  generally 
coated  with  su^huiMiga*41ie  source  of  the  spring,  forming  tufts  of 
bright  yellow  filaments  resembling  skeins  of  silk,  vibrating  with  the 
eddies 'and  currents  of  the  stream.  Farther  from  the  source  these 
threads  are  not  sulphur-coated,  but  are  encrusted  with  carbonate  of 
lime,  and  they  form  the  radiating,  fan-like  masses  of  travertine 
shown  in  Fig.  52.  The  white  algae  are  generally  found  in  the 


FIG.  53.  Coating  specimens,  Mammoth  Hot  Springs. 


rapid  currents  of  overflow  streams  ;  rarely  in  the  eddying  waters  of 
the  hot-spring  bowls. 


WEED.] 


DESCRIPTION    OF    THE    VEGETABLE    GROWTH. 


635 


It  was  suspected  that  this  white  or  sulphur-coated  species,  so 
abundant  in  the  hotter  waters,  might  be  identical  with  other  and 
more  brightly  colored  algae,  which  had  not  been  bleached  by  the  hot 
sulphurous  water.  Specimens  of  a  dark  emerald-green  growth  were 
therefore  placed  in  the  overflow  of  a  hot  sulphur  spring  alongside 
of  the  white  sulphur-coated  filaments.  In  a  few  hours  the  green 
color  had  disappeared  from  the  submerged  portion  of  the  green 
growth,  and  the  white  bleached  filaments  were  partially  coated  with 
sulphur.  Subsequent  observations  proved,  however,  that  the  white 
species  maintains  its  character  in  comparatively  cool  waters,  where 
it  occurs  associated  with  red  and  with  green  algae,  so  that  the  experi- 
ment does  not  show  the  identity  of  the  species,  as  was  at  first  sup- 
posed. xThe  green  algse  are  not  such  active  travertine  formers  as 
the  \yiiite)and  red  species.  They  thrive  best  in  the  shade,  or  where 
hidden  from  the  light  by  a  covering  of  the  red  algae,  and  the  rich 
emerald-green  color  of  the  species  changes  to  an  olive  or  dull  brown 
where  exposed  to  direct  sunlight.  Flowing  water  seems  to  be  neces- 
sary for  its  best  development,  so  that,  unlike  the  red  algae,  the  green 
species  is  seldom  found  on  the  bottom  of  overflow  pools  and  basins. 
In  water  too  hot  for  the  full  development  of  this  alga,  the  growth  is 
pale,  yellowish  green  in  color,  or  even  bright  yellow,  frequently 
occurring  in  gelatinous  masses  showing  no  trace  of  filaments.  In 
cooler  water  the  color  deepens  to  a  rich  emerald. 

The  orange  or  red  algae  are  very  active  in  the  formation  of  traver- 
tine, and  there  is  not  an  overflow  slope  that  does  not  show  traces  of 
its  color.  It  tints  the  bottoms  of  the  basins  about  the  springs,  and 
their  rims  and  walls,  with  its  varying  shades  of  yellow,  red,  or  brown, 
and  it  is  this  growth  that  imparts  the  tawny  yellow  or  orange  color 
to  the  slopes  about  all  the  springs,  particularly  noticeable  on  the 
slopes  overflowed  by  the  waters  of  the  Main  Spring.  This  species  is 
rarely  found  free  from  lime,  which  generally  incrusts  it  so  thickly 
that  it  is  difficult  to  distinguish  its  vegetable  nature. 

DESCRIPTION   OF   THE    VEGETABLE   GROWTH. 

The  springs  at  the  foot  of  the  slope  below  the  Pulpit  Basins 
formerly  presented  the  most  luxuriant  algous  vegetation  of  the  lo- 
cality, in  the  area  overflowed  by  their  waters.  This  overflow  is  now 
'  chiefly  used  to  supply  the  military  stables,  but  formerly  covered  the 
flat  north  of  the  springs,  flowing  over  a  cushion  of  algous  jelly 
several  inches  thick.  The  temperature  of  the  spring  was  127°  F., 
and  the  channel  near  it  was  filled  with  a  bubbly,  gelatinous  vegeta- 
tion, emerald  save  at  the  edges,  where  it  shaded  into  a  dull,  greenislL. 
brown.  This  changed  gradually  to  a  mix 
where  the  temperature  had  fallen  to  H5^bui  at  HQ°the  surface  of 
the  jelly  showed  no  trace  of  green,  and  the  orange  speCies  uiily  was" 
seen,  continuing  abundant  until  at-97\F.  the  growth  ceased.  Traver- 


636  FORMATION    OF    HOT    SPRING    DEPOSITS. 

tine  deposition  was  taking  place  most  rapidly  where  the  temperature 
*i  *V  £  was  (100° _J\ ,  and  the  algse  were  so  heavily  coated  and  inclosed  by  the 
deposit  that  its  organic  character  was  completely  hidden,  the  light 
salmon-red  color  being  apparently  due  to  some  mineral.  It  should 
be  mentioned  in  this  connection  that  these  springs  contain  much  less 
lime  in  solution  than  the  other  springs  of  this  locality,  and  the 
waters  do  not  coat  and  incrust  articles  placed  in  their  spray.  Only 
a  small  part  of  the  overflow  seems  to  have  run  over  this  salmon-colored 
crust,  for  upon  tearing  off  this  coating  the  inside  is  seen  to  consist 
,  of  green  algse,  the  larger  part  of  the  overflow  running  through  this 
vegetable  conduit. 

The  association  of  the  different  species  is  well  illustrated  in  their 
occurrence  at  the  Orange  Spring.  This  vent  has  built  up  a  mound 
15  feet  high,  20  to  25  feet  wide,  and  50  feet  long,  with  a  gently  arched 
summit  and  steeply  sloping  sides.  The  water  issues  from  several 
little  cones  on  the  summit,  situated  along  a  line  corresponding  to  the 
major  axis  of  the  mound,  but  there  is  usually  one  vent  from  which 
the  greatest  part  of  the  overflow  issues,  and  generally  in  a  jet  nearly 
a  foot  high.  The  temperature  is  but -148°  F.,  so  that  this  spouting  is 
"^  due  to  gaseousor  to  hydrostatic  pressure.  Falling  into  a  little  basin 
the  water  flows  off  in  a  ramifying  network  of  little  channels  to  the 
edge,  where  spreading  out  it  forms  a  thin,  glistening  sheet,  dashing 
and  rippling  down  the  steep  slopes,  only  to  sink  in  the  porous  traver- 
tine at  the  base  of  the  mound.  The  water  has  a  strong  sulphurous 
odor,  and  the  deposit  about  the  vent  contains  considerable  sulphur. 
If  under  water  the  surface  of  this  deposit  is  black,  with  bunches  of 
sulphur-coated  filaments  attached  to  the  sides  and  bottom  of  the 
channel.  Near  the  vent  these  are  the  only  algse  present,  but  pale 
yellowish  green  threads  are  found  in  the  cooler  water  at  the  border 
x-7/  // ^.A- o£"fchjS. .jghannel,  and  are  abundant_at_J.300  in  many  of  the  branch 
1  streamlets.  As  the  waTer  cooTs^tilTniore  the  green  growth  becomes 
deeper  in  color,  and  the  red  species  appears  at  the  edge  of  the  stream.  . 
This  growth  is  sometimes  filamentary,  but  generally  a  jelly-like 
membrane,  when  not  buried  in  the  travertine.  The  surface  of  the 
mound  between  the  reticulated  channels  is  covered  with  a  gelatinous 
coating  of  red  and  green  algse  similar  to  those  just  mentioned,  but 
mixed  with  crusts  of  carbonate  of  lime.  Mushroom-shaped  forms  of 
salmon-colored  travertine  rise  from  the  bed  of  the  larger  channels 
or  project  over  the  edges  of  the  stream  ;  these  are  formed  partly  by 
algse  and  partlyjpy  evaporation. 

The  steep  rounded  or  step-like  slopes  of  the  mound  are  bright 
orange  in  color  where  covered  by  the  water,  and  it  is  undoubtedly 
^_       this  which  gave  the  name  to  the  spring.     This  coloring  is  ^ue  to 
_ajg^e_similar  to  those  found  on  the  summit  of  the  mound,  but  the 
filaments  are  buried  in  the  travertine,  their  tips  alone  projecting,  re- 
minding one  of  the  growing  points  of  peat  mosses  whose  stems  can 


WEED.]  SOLUBILITY    OF    CARBONATE    OF    LIME.  637 

be  followed  down  into  the  peat  beneath.  Where  the  overflow  has 
become  too  cool  to  support  the  orange  algse,  which  does  not  live 
below  90^F.?  ajbrpwii  sp^cies-Joraas^arsmooth  veiTetytJOBting'  on  thlT 


travertine,  and  is  very  abundant  at  85_^F.  ;  this  in  turn  disappears  as 
the  water  becomes  still  cooler. 

In  the  overflow  basins  of  the  Blue  Springs  (Plate  LXXVIII)  the 
colors  of  adjoining  pools  are  often  quite  different.  In  one  of  the  hot- 
ter basins  where  the  temperature  was  142°  the  algse  tinting  the  deposit 
were  a  bright  lemon  yellow,  while  the  rich,  deep  red  growth  of  the 
adjoi-ning  basin  lived  at  115°  F.  The  red  growth  is  very  prominent 
in  water  between  110°  F.  and  130°  F.  At  the  edge  of  a  pool  where  the 
flow  was  comparatively  quiet,  a  pistachio  green  growth  merging  into 
yellow  and  orange  began  at  145°  F.,  the  growth  being  thin  and  closely 
adherent.  Close  by  a  place  where  the  flow  was  very  sluggish,  at  a 
temperature  of  130°  F.  ,  the  orange  algse  are  abundantly  developed 
in  gelatinous  balloon-Jike  forms.  At  115°  F.  the  red  tint  is  much 
browner  and  at  95°  F.  is  a  dark  orange  brown. 

In  several  of  the  basins,  yellow,  red,  salmon,  green,  and  brown 
interblend,  owing  to  differences  in  depth  and  consequently  in  tem- 
perature and  current.  The  vegetable  nature  of  such  growths  is  gen- 
erally much  obscured  by  the  accompanying  deposition  of  travertine. 

SOLUBILITY   OF   CARBONATE   OF  LIME  IN  NATURAL  WATERS. 

The  large  amount  of  carbonate  of  lime  which  the  hot  waters  of  the 
Mammoth  Hot  Springs  contain  in  solution  suggests  an  inquiry  regard- 
ing the  conditions  under  which  such  waters  take  that  salt  into  solution. 

In  pure  water  the  carbonate  of  lime  is  very  sparingly  soluble,  the 
proportion  given  by  Bineau  being  but  one  part  in  30,000.  to  one  in 
50,000,  or  according  to  Fresenius,  one  part  in  10,800  cold  and  8,875 
parts  of  boiling  water.  In  carbonated  waters  the  neutral  carbonate 
of  lime  unites  with  the  carbonic  acid  to  form  the  bicarbonate  of 
lime,  which  is  readily  dissolved  in  water  to  the  extent  of  0.  88  grammes 
per  litre  in  water  saturated  with  carbonic  acid  gas  at  the  ordinary 
atmospheric  pressure  and  a  temperature  of  10°  C.  With  an  increase 
of  pressure  the  amount  taken  into  solution  is  augmented  with  the 
increase  of  carbonic  acid  absorbed,  but  the  maximum  amount  that  can 
be  dissolved  is  about  3  grammes  per  litre.  '  The  presence  of  alkaline 
and  earthy  salts  in  water  free  from  carbonic  acid  favors  the  forma- 
tion of  unstable  supersaturated  solutions  of  carbonate  of  lime,  from 
which  the  lime  is  gradually  precipitated,  this  separation  being  more 
rapid  from  waters  containing  the  chlorides  than  from  those  holding 
the  sulphates  of  the  alkalies  and  the  alkaline  earths.  Magnesium 
sulphate  and  sodium  sulphate  form  solutions  with  a  certain  amount 
of  stability,  but  the  lime  is  all  precipitated  in  eight  to  ten  days.' 

1  Roscoe  and  Schorlemmer,  vol.  2,  p.  208. 

8  T.  Sterry  Hunt  :  Am.  Jour.  Sci.  ,  3d  series,  vol.  42,  p.  58. 


638  FORMATION    OF    HOT    SPRING    DEPOSITS. 

In  water  saturated  with,  carbonic  acid  the  alkaline  and  earthy  chlo- 
rides form  unstable  supersaturated  solutions,  from  which  the  lime 
soon  crystallizes  out  as  the  hydrous  carbonate  (at  low  temperatures) 
and  the  solution  then  contains  but  0. 8  grammes  of  carbonate  of  lime 
per  litre,  corresponding  to  that  dissolved  by  the  carbonic  acid. '  But 
the  capacity  of  carbonated  waters  for  carbonate  of  lime  is  nearly 
doubled  by  the  presence  of  magnesium  sulphate  or  sodium  sulphate 
in  the  solution.  Water  holding  either  of  these  sulphates  in  solution 
in  the  proportion  of  T£oth  or  even  less,  and  impregnated  with  car- 
bonic acid,  readily  takes  into  permanent  solution  at  the  ordinary 
temperatures  and  pressure  a  quantity  of  pure  carbonate  of  lime 
equal  to  1.56  to  1.82  and  even  2  grammes  to  the  litre.3  It  is  thus  evi- 
dent that  solutions  of  carbonate  of  lime  in  pure  or  mineral  waters 
are  permanent  only  in  the  presence  of  free  carbonic  acid. 

CHARACTER   OF   THE   HOT   SPRING  WATERS. 

The  water  of  the  Mammoth  Hot  Springs  is  remarkably  clear  and 
transparent ;  the  temperature  varies  at  different  springs  from  80° 
F.  up  to  165°  F.,  exceeding  130°  in  all  the  larger  springs.  While  hot 
it  generally  possesses  a  sulphurous  odor,  the  intensify  varying  greatly 
at  different  springs,  but  always  being  strong  if  the  temperature  ex- 
ceeds 140°,  when  sulphur  is  found  incrusting  the  algse  filaments 
growing  near  the  vent  of  the  spring.  When  cold  the  water  is  not 
peculiar  in  taste  or  in  odor,  but  it  is  considered  unfit  for  drinking, 
owing  to  the  large  amount  of  carbonate  of  lime  which  it  holds'  in 
solution. 

At  many  of  the  springs  a  large  amount  of  gas  escapes  as  the  water 
issues  from  the  vent,  which  is  proven  by  analysis  to  consist  of  car- 
bonic acid  gas,  oxygen,  and  nitrogen.  Although  the  odor  of  sulphur 
is  very  noticeable  and  sulphur  is  deposited  at  many  of  the  springs, 
the  amount  of  sulphuretted  hydrogen  present  in  the  water  is  very 
small,  and  is  too  minute  to  appear  in  the  analysis  of  the  waters. 
The  general  character  of  the  water  is  the  same  in  all  the  springs,  but 
the  amount  of  mineral  matter  held  in  solution  varies  at  different 
springs  from  15  to  17  parts  in  10,000,  and  of  this  one-third  consists  of  • 
carbonate  of  lime  and  the  remainder  of  readily  soluble  salts. 

In  the  following  table  analyses  are  given  of  typical  waters  from 
the  Mammoth  Hot  Springs,  and  also  of  the  surface  waters  of  the 
surrounding  slopes.  These  analyses  were  made  by  Prof.  F.  A. 
Gooch  and  J.  E.  Whitfield,3  for  the  Geological  Survey  of  the  Yel- 
lowstone National  Park.  In  the  same  table  analyses  for  compar- 
ison are  given  of  the  thermal  waters  of  Hierapolis  and  Kukurtlu, 

1  Hunt.  loc.  cit.  and  Skey,  in  Trans.  New  Zealand  Inst. ,  vol.  9,  p.  454 

2 Hunt,  loc.  cit.,  p.  50. 

'Analyses  of  Waters  of  the  Yell.  Nat.  Park,  Bull.  No.  47,  U.  S.  Geol.  Survey. 


WEED.] 


ANALYSES    OF   THE    HOT    SPRINGS    WATER. 


639 


Asia  Minor,  made  by  J.  Lawrence  Smith,1  and  also  of  the  Carlsbad 
sprudel,  made  by  Ragksy.2 

Analyses  of  waters  from  the  Mammoth  Hot  Springs. 


Cleo- 
patra. 

Orange. 

136°  F. 
Hot 
River. 

Gardi- 
ner. 

Hotel 
water. 

130°  F. 
Hiera- 
polis. 

182°  F. 

Carls- 
bad. 

0  0009 

0.020 

NH4C1  
LiCl 

0.0019 
0  0140 

0.0097 

0.0003 
0.0068 

Trace. 

Na  Cl 

0  1903 

0.1636 

0.  1855 

1.0306 

K  Cl 

0  0976 

0.  1165 

0.0882 

0  0103 

0.0046 

K  Br 

Trace 

Trace 

Na2  SO4  

0.1448 

0.1834 

0.2265 

0.  0161 

0.0448 

0.341 

0.  1950 

2.  3721 

K2  SO4 

0  0056 

0  0015 

0  0202 

0.1636 

Mg  SO4 

0  3645 

0  3295 

0  3155 

0  0076 

0.431 

Ca  SO4  

0.  1953 

0.2002 

0.1450 

0.119 

0.  1710 

A12  (SO4)3  

0.0043 

Na2  B4  O7  
Na  As  O2  
Ca  CO3            

0.0326 
0.0041 
0.6254 

0.5580 

0.0185 
0.0004 
0.4833 

0.0625 

0  0790 

*1.368 

*0.  1830 

0.2978 

Mg  CO3      

0  0018 

0  0258 

*0.041 

*0.0460 

0.1240 

NaHCO3  
Fe  CO3             

tO.  0340 

0.078 

tl.3619 
0.0028 

Mn  CO3      

0  0006 

A12  O3       

0.0093 

.0022 

0.0097 

0  0079 

0  0021 

JO  0004 

Si  O2 

0.  0517 

0  502 

0  0500 

0  0469 

0  0355 

0  008 

0  1100 

0  0728 

Total  solids.  ... 

1.7315 

1.6183 

1.5297 

1.934 

0.970 

5.  4312 

Total  COa  §  ... 

0.3537 

.0924 

0.2143 

0  0286 

0  0748 

(0  3520) 

0  7604 

Summation  .... 

2.0852 

1.7057 

1.7440 

0.  2137 

0.2757 

*  Bicarbonate. 


t  Neutral. 


iAla(P04)a. 


§  Free. 


The  analyses  show  that  the  amount  of  carbonate  of  lime  held  in 
solution  in  waters  of  the  Mammoth  Hot  Springs  is  greatly  in  excess 
of  that  which  the  carbonic  acid  of  the  water  is  capable  of  dissolving. 
In  the  Cleopatra  water,  which  contains  the  greatest  amount  of  car- 
bonate of  lime,  viz,  0.6254  parts  in  1,000,  the  excess  of  carbonic  acid 
over  that  necessary  to  form  the  neutral  carbonate  is  0.3537  gramme 
per  litre.  If  this  were  united  to  form  bicarbonates,  the  excess  of 
free  carbon  dioxide  would  be  but  0.0786  gramme.  But  as  water  sat- 
urated with  carbonic  acid,  that  is,  containing  2  grammes  per  kilo- 
gramme, will  dissolve  but  0.88  gramme  carbonate  of  lime,  the  pro- 
portionate amount  dissolved  by  0.3537  gramme  of  carbonic  acid  will 
be  0.1552  gramme  of  carbonate  of  lime.  Since  the  water  actually 
contains  0. 6254  gramme  of  carbonate  of  lime  in  solution  in  each  kilo- 
gram of  water,  there  is  an  excess  of  0.4698  gramme  of  carbonate  of 
lime  which  has  been  dissolved  either  by  increased  pressure  or  by 
the  alkaline  salts  present.  As  the  water  has  been  under  pressure, 

1  Original  Researches,  p.  63. 

2 Carlsbad,  Marienbad,  etc.,  u.  ihre  Umgebung  :  Prag  1862,  p.  76. 


640  FORMATION    OF    HOT    SPRING    DEPOSITS. 

which  was  relieved  as  it  rose  to  the  surface,  this  has  probably  influ- 
enced the  solution  of  the  carbonate  of  lime,  but  the  effect  of  the 
salts  present  is  undoubtedly  very  important. 

The  Hierapolis  waters  contain  0. 937  gramme  of  carbonate  of  lime 
per  kilogram,  considerably  more  than  the  Cleopatra  water,  with 
0.3520  gramme  of  carbonic  acid  which  can  dissolve  but  0.1549  gramme 
of  carbonate  of  lime,  leaving  0.7820  gramme  of  the  latter  to  be  dis- 
solved by  the  0.772  gramme  of  magnesium  and  sodium  sulphates 
present,  combined  with  the  increased  pressure  under  which  the 
water  existed  before  reaching  the  surface. 

The  Cleopatra  water  is  supersaturated  as  it  issues  from  the  spring, 
since  it  deposits  a  small  amount  of  calcic  carbonate  upon  standing 
in  tightly  stoppered  bottles.  This  supersaturation  is  probably  due  to 
the  relief  of  pressure  as  the  water  rises  in  the  tube  of  the  spring  and 
issues  from  the  vent.  As  the  water  flows  over  the  travertine  slopes 
and  basins  there  is  a  loss  of  carbonic  acid  and  a  deposition  of  car- 
bonate of  lime.  At  the.  same  time  the  water  is  concentrated  by 
evaporation  owing  to  the  large  surface  exposed.  A  small  sample  of 
water  was  collected  from  the  slopes  of  the  mound  of  the  Cleopatra 
spring,  at  a  point  25  feet  below  and  distant  50  feet  horizontally  from 
the  point  of  issue.  The  water,  in  flowing  this  distance,  had  cooled 
from  156°  F.  down  to  113°  F.,  and  had  lost  4  per  cent  by  evaporation, 
This  result  is  reached  by  a  comparison  of  the  sulphuric  acid  found 
in  the  water  of  the  spring  with  that  in  the  water  of  the  slope.  Cor- 
recting for  evaporation,  a  comparison  of  the  analysis  with  that  of  the 
spring  water  shows  a  loss  of  0.2251  gramme  per  kilogram  of  carbonic 
acid  by  diffusion,  and  the  deposition  of  0.1675  gramme  of  carbonate 
of  lime  in  flowing  this  short  distance.  Notwithstanding  the  depo- 
sition of  this  amount  of  calcium  carbonate,  the  water  was  super- 
saturated with  that  salt,  for  it  deposited  carbonate  of.  lime  upon 
standing  in  a  tightly  stoppered  bottle,  probably  because  of  the  loss 
of  the  carbonic  acid  and  the  concentration  of  the  water  in  flowing 
down  the  slope. 

-       DEPOSITION  OF   CARBONATE   OF   LIME. 

As  the  presence  of  carbonic  acid  gas  is  essential  to  the  permanence 
of  a  solution  of  carbonate  of  lime,  whether  the  solution  contains 
alkaline  and  earthy  salts  or  not,  the  withdrawal  of  the  carbonic 
acid  will  cause  a  supersaturation  of  the  liquid  with  a  gradual  separa- 
tion and  precipitation  of  the  lime  carbonate.  Thus  deposits  of  car- 
bonate of  lime  may  be  due  to  the  following  causes  : 

(1)  Relief  of  pressure. 

(2)  Diffusion  of  the1  carbonic  acid  by  exposure  to  the  atmosphere. 

(3)  Evaporation. 

(4)  Heating. 

(5)  Influence  of  plant  life. 


WEED.]  -    DEPOSITION    OF    CARBONATE    OF    LIME.  641 

Where  the  solution  has  been  formed  under  pressure,  the  increased 
amount  of  carbonic  acid  which  the  water  is  then  capable  of  retaining 
permits  the  solution  of  a  larger  amount  of  carbonate  of  lime.  Upon 
the  relief  of  this  pressure  the  excess  of  gas  escapes,  and  an  unsta- 
ble, supersaturated  solution  results,  from  which  the  lime  carbonate 
gradually  separates  out.  In  this  way  originates  the  troublesome 
incrustations  inside  the  pipes  of  pumps,  and  the  saturation  of  many 
spring  waters  is  undoubtedly  due  to  the  relief  of  pressure  as  the 
water  issues  from  the  ground. 

Richly  carbonated  waters  lose  a  portion  of  their  carbonic  acid  upon 
exposure  to  the  air ;  simple  standing  is  sufficient  to  cause  the  separa- 
tion of  lime  carbonate  upon  the  surf  ace  of  pools  of  such  solutions,  and 
the  diffusion  of  the  carbonic  acid  is  proportionate  to  the  temperature. 
Deposits  formed  in  this  way  are  common  on  the  bottom  of  stagnant 
basins  at  the  Mammoth  Hot  Springs,  where  the  pellicle  of  carbonate 
of  lime  forming  upon  the  surface  breaks  up  on  thfckening,  and  fall- 
ing to  the  bottom  accumulates  as  a  flaky,  loose  deposit.  This  diffu- 
sion of  carbonic  acid  gas  by  exposure  to  the  air  is  greatly  facilitated 
by  increasing  the  surface  exposed,  as  well  as  by  the  agitation  of  the 
water ;  this  is  the  case  where  the  water  spreads  out  over  a  surface  in 
a  thin  sheet,  or  in  cascades  and  spray.  This  diffusion  is  generally 
accompanied  in  such  cases  by  evaporation,  which  also  produces  a 
separation  of  the  lime  carbonate.  Stalactites,  and  similar  formations 
common  in  limestone  caves,  are  produced  by  these  causes  acting 
simultaneously,  and  the  "petrified"  or  really  incrusted  bouquets, 
baskets,  etc. ,  of  Carlsbad  and  many  European  springs,  and  also  the 
Mammoth  Hot  Springs,  are  covered  with  crystals  of  calcite  deposited 
in  this  wa.y.  (Fig.  53.) 

Evaporation  alone  causes  the  formation  of  deposits  of  lime  car- 
bonate, in  the  form  of  tufa,  by  a  concentration  and  supersaturation 
of  the  water.  Such  deposits  are  of  great  extent  about  several  of  the 
lakes  of  the  Great  Basin,  as  described  by  King,  and  Hague,1  and 
lately  by  I.  C.  Russell.8 

Heat  causes  a  precipitation  of  the  lime  carbonate  by  a  double  action, 
driving  off  the  carbonic  acid  and  diminishing  the  solvent  effect  of 
the  alkaline  and  earthy  salts  present,3  resulting  in  the  formation  of 
boiler  scale  and  incrustations  where  lime-bearing  water  is  used  for 
generating  steam. 

Deposits  of  carbonate  of  lime  are  also  formed  from  natural  waters 
by  chemical  reaction,  as  in  the  case  of  the  tufa  cones  and  tubes  formed 
about  the  sublacustrine  springs  of  Mono  Lake. 4 

1  Geol.  Explor.  of  the  40th  Par.:  vol.  1,  p.  514 ;  vol.  2,  p.  822. 
"LakeLahontan:  Monograph  No.  11,  U.  S.  Geol.  Survey. 
3Skey  :  Trans.  New  Zealand  Inst.,  vol.  10,  p.  449. 
4  Russell,  loc.  cit. 

9   GEOL 41 


642  FORMATION    OF    HOT    SPRING    DEPOSITS.  - 

DEPOSITS   OF  CARBONATE  OF  LIME   DUE  TO   PLANT    LIFE. 

In  the  formation  of  the  deposits  just  discussed,  it  is  evident  that 
plant  life  takes  no  part.  It  has,  however,  been  long  known  that  many 
water  plants  possess  the  power  of  abstracting  carbonate  of  lime  even 
from  waters  exceedingly  poor  in  this  salt,  as  in  the  case  of  sea  water, 
where  the  Corrallines  and  other  marine  algae  build  their  framework 
of  lime  carbonate.  Many  fresh  water  plants,  especially  the  CharcB 
and  some  mosses,  also  produce  a  separation  of  carbonate  of  lime. 
Our  knowledge  of  this  subject  is  chiefly  due  to  the  researches  of  Dr. 
Ferd.  Cohn,  who  has  shown  the  life  of  mosses  and  of  algse  to  be  a 
most  energetic  factor  in  the  formation  of  deposits  of  travertine. 

The  warm  mineral  waters  of  Carlsbad  contain  an  abundant  algous 
vegetation  which  forms  thick  cushions  of  jelly  on  the  sides  of  the 
stream  channels  and  generally  wherever  the  warm  waters  flow. 
The  association  of  this  growth  with  the  deposition  of  travertine  is 
very  striking,  and  early  writers  upon  the  vegetation  of  the  springs 
called  certain  species  lime-incrusted.  Dr.  Cohn  was  the  first  to  dis- 
cover the  true  relation  of  this  plant  life  to  travertine  deposition, 
and  in  a  paper  published  in  1862  he  showed  that  these  algse  actually 
eliminate  carbonate  of  lime  from  the  water  and  form  travertine.1 
In  proof  of  this  he  states  that  if  a  part  of  the  algous  jelly  be  pressed 
between  the  fingers  an  extremely  fine  sand  is  felt  between  the  tips 
of  the  fingers,  the  grains  being  much  larger  if  the  jelly  is  taken 
from  the  older  and  lower  parts  of  the  growth.  The  nature  of  this 
sand  and  its  true  relation  to  the  vegetable  tissue  are  easily  recog- 
nizable, the  microscope  showing  minute  crystals  of  carbonate  of  lime 
in  the  slime  between  the  vegetable  threads  and  upon  their  surface. 
These  crystals,  which  at  first  are  separate,  increase  in  number  and 
form  star-like  clusters,  which  by  enlargement  grow  into  grains  of 
calcareous  sand.  By  the  further  deposition  of  carbonate  of  lime 
these  grains  grow  together  and  are  cemented  into  solid  travertine. 
All  these  steps  are  said  to  be  recognizable  under  the  microscope  with 
the  aid  of  hydrochloric  acid. 

The  explanation  of  this  deposition  of  lime  carbonate  within  and 
upon  the  vegetable  tissue  is  said  to  be  the  physiological  action  of 
the  plant,  jvhich  by  withdrawing  carbonic  acid  from  the  water  dimin- 
ishes the  amount  of  carbonate  of  lime  which  it  is  capable  of  retain- 
ing in  solution,  the  excess  crystallizing  out  in  the  manner  described. 
The  supply  of  the  soluble  bicarbonate  of  lime  withdrawn  from  the 
water  by  this  double  action  of  the  plant  is  renewed  by  endomatic 
circulation.  The  cementing  together  of  the  grains  of  sand,  which 
takes  place  in  the  older  and  deeper  layers  of  the  algous  mass,  is 

1  Die  Algen  des  Karlsbader  Sprudels,  mit  Rticksicht  auf  die  Bildung  des  Sprudel 
sinters:  Abhandl.  der  Schles.  Gesell.  pt.  2  Nat.,  1862,  p.  35. 


WEED.]  PLANTS    AS    KOCK    BUILDERS.  643 

thought  to  be  largely  due  to  a  process  independent  of  plant  life,  in 
which  the  porosity  of  the  tufa  plays  a  part. 

The  exact  relation  of  the  crystals  and  grains  of  carbonate  of  lime 
varies  in  the  different  species  of  algae.  In  the  Oscillarice  of  Carlsbad, 
and  allied  species,  the  crystals  form  in  the  slimy  inter-cellular  tissue; 
in  Halimeda,  the  carbonate  of  lime  forms  a  sieve-like  cover  about 
the  tips  of  the  algse  filaments,  and  in  Acchihtria  it  occurs  as  a  tube 
about  the  stalk  of  the  plant.  In  the  Charm  the  lime  is  separated 
and  deposited  in  the  cells  and  cell  walls  of  the  back  alone,  while  in 
the  Corallines  it  is  found  only  within  the  cells. 

It  has  already  been  stated  that  the  algous  vegetation  of  the  Mam- 
moth Hot  Springs  also  produces  a  separation  of  carbonate  of  lime. 
A  careful  study  of  this  vegetation  in  the  field  and  under  the  micro- 
scope shows  that  this  process  is  similar  to  that  discovered  by  Dr. 
Cohn.  At  Carlsbad  it  was  found  that  no  vegetation  was  present  and 
no  tufa  was  deposited  where  the  temperature  exceeded  131°  F.  (44° 
R.),  but  with  the  appearance  of  algae  in  the  water  the  deposition  of 
travertine  began.  A  similar  statement  can  not  be  offered  in  proof 
of  the  influence  of  such  growths  in  the  deposition  of  carbonate  of 
lime  at  the  Mammoth  Hot  Springs,  for  one  species  of  algse  is  found 
at  165°  F.,  the  hottest  water  of  this  locality.  But  that  the  algae  of 
these  springs  secrete  carbonate  of  lime  and  form  travertine  can  be 
satisfactorily  demonstrated,  and  the  process  may  be  observed  wher- 
ever the  hot  waters  flow. 

Masses  of  gelatinous  vegetable  growth,  closely  resembling  those 
of  the  Carlsbad  sprudels,  are  found  about  many  of  the  springs, 
notably  those  at  the  north  base  of  Capitol  Hill  and  at  the  Jupiter 
Springs.  In  this  vegetable  jelly  thin  and  flaky  layers  of  carbonate 
of  lime  are  found  in  the  plant  tissue.  An  examination  of  this  gelat- 
inous substance  shows  that  it  is  composed  of  successive  membrane- 
like  sheets,  in  which  minute  gritty  particles  can  be  felt  with  the 
fingers.  Under  the  microscope  isolated  little  crystals  and  stellate 
accretions  of  these  crystals  are  found  scattered  about  in  the  plant 
tissue.  These  by  further  growth  form  minute  grains  of  carbonate 
of  lime.  In  the  older  layers  and  on  the  surface  of  this  flaky  traver- 
tine all  sizes  of  grains  are  found,  the  largest  being  one  millimeter  in 
diameter. 

This  deposit  is  made  up  of  these  pellets,  plainly  seen  in  the  freshly 
formed  tufa  layers,  but  indistinguishable  in  the  older  layers,  where 
the  grains  are  cemented  together  and  the  oolitic  structure  is  lost. 
This  cementation  of  these  pellets  and  of  the  thin  laminae  forms  a 
firm,  more  or  less  compact,  travertine.  The  membranous  structure 
of  the  Carlsbad  growth  is  supposed  to  be  due  to  the  intermediate  or 
intercalated  layers  of  carbonate  of  lime,  ascribed  to  a  certain  period- 
icity of  outflow  from  the  spring,  the  temperature  being  constant. 
The  same  structure  found  at  the  Mammoth  Hot  Springs  is  not  neces- 


644  FORMATION    OF    HOT    SPRING    DEPOSITS. 

sarily  due  to  this  cause,  since  alterations  in  the  amount  and  temper- 
ature of  the  current  nourishing  the  algse  may  be  caused  by  the 
obstructive  growth  of  the  plants  themselves,  which  thus  produces  a 
change  in  both  the  vegetation  and  the  deposit.  In  addition  to  this, 
evaporation  and  loss  of  carbonic  acid  from  the  water  flowing  over 
the  surface  of  the  growth  cause  the  formation  of  a  crust  of  carbonate 
of  lime,  which  is  afterwards  covered  by  alga3,  as  the  water  dammed 
by  the  growth  below  is  forced  to  flow  over  this  surface. 

If  the  water  supply  be  cut  off  from  a  mass  of  such  algous  growth 
the  plants  die,  the  green  changes  to  brown,  and  this  to  rose  pink, 
and  finally  to  a  light  salmon,  while  the  odor  of  decaying  vegetable 
matter  is  very  perceptible.  In  a  short  time  all  color  fades  from  the 
surface  and  a  soft  and  porous  chalky  deposit  is  all  that  remains  of 
the  mass  of  jelly-like  algous  growth.  If  a  little  moisture  is  present 
the  pink  tint  remains  a  long  time,  and  is  generally  noticeable  in  the 
inner  parts  of  the  deposit.  Such  areas  are  common  at  the  Mammoth 
Hot  Springs,  especially  about  the  changing  vents  of  sulphur  springs, 
and  at  numerous  places  where  warm  waters  have  issued  from  little* 
vents  early  in  the  season,  but  have  dried  up  on  the  advance  of  sum- 
mer, leaving  this  pink  tinted  and  soft  deposit  as  the  only  evidence 
of  the  recent  outflow. 

As  already  mentioned,  the  escape  of  carbonic  acid  and  the  evapo- 
ration of  the  water  are  very  rapid  on  the  overflow  slopes,  below  the 
Main  Springs.  In  consequence  of  this,  a  coating  of  pure  white  crys- 
talline carbonate  of  lime  is  rapidly  deposited  upon  objects  of  any 
kind  placed  in  the  spray  of  the  hot  water,  a  thickness  of  ^V  to  ^  of 
an  inch  being  formed  in  three  days  under  favorable  circumstances. 
This  incrusting  property  of  the  water  is  utilized  for  the  production 
of  coated  "specimens,"  made  to  sell  to  tourists.  Horseshoes,  pine- 
cones,  bottles,  and  different  forms  of  wire  work  are  placed  on  rude 
racks,  or  suspended  from  the  cross-bars  of  the  rack  by  strings  and 
the  hot  water  led  over  them  so  that  the  objects  to  be  coated  are  con- 
stantly wetted  by  the  hot  spray,  as  shown  in  Fig.  53.  The  deposit  so 
formed  is  pure  white  and  marble-like,  and  the  little  crystals  sparkle 
in  the  light.  If,  however,  the  objects  be  permitted  to  remain  in  the 
spray  several  days  longer,  the  deposit  loses  its  intense  whiteness  and 
assumes  a  dull  yellowish  tint.  At  the  same  time  the  former  smooth 
surface  of  the  coating  is  dotted  with  wart-like  excrescences  which  be- 
come larger  and  more  numerous  the  longer  the  specimen  is  exposed, 
and  in  time  will  distort  and  disguise  the  original  shape  of  the  object, 
while  the  color  becomes  a  rich  umber  brown.  By  treating  specimens 
of  this  character  with  dilute  hydrochloric  acid  these  changes  are 
seen  to  be  due  to  the  growth  of  algae.  The  first  points  of  growth 
are  places  of  most  rapid  deposition,  and  warty  excrescences  are 
formed ;  later  the  alga3  are  present  all  over  the  surface  and  the  thick 
coating  becomes  dendritic  in  structure,  and  both  color  and  form  sug- 


WEED.]  DESCRIPTION    OF    THE    DEPOSITS.  645 

gest  organic  life.  In  such  deposits  vegetable  life  is  not,  however, 
the  only  factor,  since  we  have  seen  that  the  water  will  deposit  a 
coating  of  carbonate  of  lime  without_thjiiniLuejica  Q£  plant  life.  But 
these  influences  are  eliminated  if  we  place  such  objects  under  water,  \ 
in  the  bowl  of  either  of  the  main  springs;  for  bottles,  horseshoes,  or 
other  articles  of  glass  or  iron  immersed  in  these  springs  for  a  long 
time  were  not  coated. 

If,  however,  a  pine  branch,  a  part  of  some  bush  or  plant,  be  placed 
under  the  water  it  is  shortly  covered  with  an  incrusting  cylinder  of 
carbonate  of  lime.  The  Surface  of  this  cylinder  is  reddish  brown 
and  warty,  resembling  the  deposit  last  mentioned ;  the  interior  is 
dendritic  in  structure  and  of  a  light  buff  color.  This  deposit  closely 
resembles  the  travertine  cylinders  formed  about  twigs  and  branches 
at  Tivoli.  In  the  formation  of  these  cylinders  at  Tivoli,  Cohn  has 
shown'  that  crystalline  sinter  is  only  separated  about  living  plants 
whose  bark  is  covered  with  growing  algae  and  mosses.  In  our  de- 
posits the  nature  of  the  substance  immersed  is  important  only 
because  it  affects  the  ability  of  the  algae  to  obtain  a  foothold  and  to 
grow,  and  the  deposition  of  sinter  is  coincident  with  the  growth  of 
such  algae. 

A  portion  of  this  deposit  dissolved  in  dilute  hydrochloric  acid 
leaves  a  residue  of  tangled  algous  filaments,  forming  a  felt-like  mass. 
The  nodular  masses  common  on  the  bottom  of  hot  water  pools  and 
basins  are  similar  in  nature  ;  the  surface  of  these  formations  is  moss- 
like,  brown  and  greenish  in  color,  particularly  in  the  depressed  por- 
tions. The  interior  is  formed  of  buff -colored  tufa  of  radiating  den- 
dritic fibers. 

DESCRIPTION  OF  THE  DEPOSITS. 

The  different  varieties  of  travertine  found  at  the  Mammoth  Hot 
Springs  vary  in  physical  structure  and  in  appearance,  according  to 
the  conditions  under  which  the  deposit  was  formed.  In  general,  the 
compactness  of  the  travertine  depends  upon  the  rapidity  of  forma- 
tion, some  of  the  most  quickly  formed  deposit  being  so  light  and 
porous  that  it  is  easily  crumbled  to  powder  between  the  fingers,  while 
the  slowest  formed  deposit  is  almost  flint-like  in  texture. 

The  travertine  of  the  oldgr^^errace^is  often  compact,  dense,  and 
hard,  resembling  an  ordinary  limestone ;  another  variety,  often  of 
recent  formation,  is  also  compact  and  crystalline,  resembling  the 
purest  of  marble ;  while  the  freshly  formed  walls  of  the  basins  of 
the  Main  Terrace  are  often  soft  and  easily  crushed.  Notwithstand- 
ing the  marked  differences  of  structure  and  appearance  the  traver- 
tine all  has  the  same  chemical  composition  as  shown  by  analysis. 

The  following  analyses,   made  for  the  Geological  Survey  of  the 

1  Neues  Jahrbuch  (Leonhard),  1864,  p.  580. 


646 


FORMATION    OF    HOT    SPRING    DEPOSITS. 


Yellowstone  National  Park,  by  Mr.  J.  E.  Wliitfield,  show  the  com- 
position of  typical  specimens  of  varying  forms  of  the  Mammoth  Hot 
Springs  deposit ;  analyses  are  also  given  of  travertines  from  other 
localities. 

Analyses  of  Travertines. 


I. 

II. 

III. 

IV. 

V. 

VI. 

VII. 

VIII. 

IX. 

SiOa  silica          .  .  . 

0  08 

0  26 

0  06 

0  01 

0  15 

0  6 

0  30 

0  12 

A12O3  +  FeaO3   

0.15 

0.11 

0.14 

0.05 

0.49 

1.10 

SOS,  sulph.  acid  
CaO,  lime  

1.72 
53  83 

1.34 
54  06 

0.70 
55.02 

0.49 
55.02 

0.55 
53  46 

0.80* 

0.08« 

CaCOj,  lime  carbon- 
ate        

*(94  97) 

*(95  77) 

*(96  02) 

*(96  02) 

*(95  36) 

96  82 

98  02 

97  00 

95  62 

MgO,  magnesia  .  . 

0.90 

0.60 

0.06 

0.07 

0.42 

0.16" 

3  06" 

Nad,  sodium  chlo- 
ride   

0.02 

0.26 

0.30 

0  12 

0  13 

KaO,  potash 

0  08° 

0  04 

0  01 

0  107 

CO2,  carbonic  acid  .  . 

41.79 

42.14 

42.25 

42.25 

41.96 

HaO,  water  

1.43 

1.19 

1.06 

1.61 

2  44 

1.30 

C,  carbon  

0.21 

None 

0.24 

0.11 

0.37 

Other  constituents  .  . 

1  41 

1  20 

Total 

100  13 

99  96 

99  81 

99  77 

99  98 

99  94 

100  00 

99  36 

99  39 

•  Sulphate  of  lime.  b  Carbonate  of  magnesia. 

*If  all  the  COa  be  supposed  to  be  combined  with  lime. 


c  Potassic  chloride 


No.  I  is  a  compact  yellowish  travertine  from  the  slopes  below  the 
Hotel  Terrace,  and  it  represents  the  older  travertine. 

No.  II  is  the  riffled  travertine  forming  the  ridge  west  of  the  Blue 
Springs  and  above  Cupid's  Cave. 

No.  Ill  is  the  fibrous  white  travertine  forming  the  fan-shaped 
masses  seen  in  the  Blue  Springs  and  elsewhere,  the  specimen  being 
from  a  deserted  vent  near  the  Blue  Springs. 

No.  IV  is  from  a  mushroom-shaped  mass,  showing  the  color  and 
structure  of  the  organic  growth  found  in  the  overflow  of  spring 
No.  24 

No.  V  is  the  crystalline  travertine  found  011  the  walls  of  Cupid's 
Cave.  The  surface  is  satiny  and  mottled,  with  spicules  and  beaded 
formations  resembling  siliceous  sinter. 

No.  VI  is  the  analysis  of  the  Carlsbad  sprudelstein  made  by  Ber- 
zelius. ' 

No.  VII  and  No.  VIII  are  travertines  from  Hierapolis  and  from 
Kukurtlu,  Asia  Minor,  analyzed  by  J.  Laurence  Smith." 

No.  IX  is  the  tufa  found  about  the  Arkansas  hot  springs,  analyzed 
by  David  Dale  Owen.3 

Though  travertine  formed  without  the  presence  and  aid  of  plant- 
life  forms  but  a  very  small  part  of  the  bulk  of  the  Mammoth  Hot 

1  Annalen  der  Physik,  Gilbert:  vol.  74,  p.  168. 
8  Original  Researches,  p.  65. 
3  Geology  of  Arkansas. 


WEED.]  DESCRIPTION    OF    THE    DEPOSITS.  647 

Springs  deposit,  there  are  two  interesting  varieties  in  the  formation 
of  which  vegetable  life  was  absent.  The  first  is  the  thin  flaky  de- 
posit found  at  the  bottom  of  stagnant  pools  and  basins  of  the  spring 
water.  This  is  formed  by  a  separation  of  calcic  carbonate  "at  the 
surface  of  the  pool,  owing  to  the  diffusion  of  carbon  dioxide  upon 
prolonged  exposure  of  the  water,  forming  a  thin  wax-like  film  upon 
the  surface ;  this  thickens  until  the  crust  breaks  up  from  its  own 
weight  and  the  flakes  settle  to  the  bottom  of  the  basin.  This  mate- 
rial is  nearly  pure  carbonate  of  lime,  whose  specific  gravity,  2.70356, 
shows  it  to  be  a  true  calcite. 

Another  variety  also  made  independently  of  plant  life  is  that 
which  forms  the  lining  of  hot-spring  chambers,  such  as  the  Devil's 
Kitchen,  and  the  spring  vent-holes.  This  is  deposited  comparatively 
slowly,  and  occurs  in  shelly  layers  half  an  inch  to  three  inches  thick, 
with  a  smooth,  rounded,  and  globular  surface.  It  is  crystalline  and 
marble-like  and  pure  white.  This  travertine  is  a  crystallization  out 
of  a  supersaturated  solution  of  carbonate  of  lime,  due  to  the  relief  of 
pressure  as  the  waters  approach  the  surface.  A  similar  deposit  lines 
the  vent-holes  of  the  Orange  and  other  springs,  and  is  analogous  to 
the  deposits  so  quickly  formed  in  the  conduit  pipes  leading  the  hot 
water  to  the  hotel  baths,  also  due  to  supersaturation,  experiments 
showing  that  such  solutions  do  not  deposit  their  excess  of  lime  at 
once,  but  in  the  course  of  a  short  time. 

All  other  varieties  of  the  travertine  so  far  found  have  been  formed 
partially  or  entirely  by  the  aid  of  plant  life.  Of  the  numerous  forms 
produced  in  this  way  there  is  none  which  shows  its  vegetable  origin 
more  clearly  than  the  fibrous  tufa  forming  the  fan-like  masses  found 
in  many  of  the  springs.  (Fig.  52.)  A  simple  examination  of  this 
deposit  with  a  lens  shows  that  the  fibers  are  neither  long  crystals 
nor  crystal  aggregates,  and  the  stringy  or  blade-like  fibers  suggest 
the  incrustation  of  vegetable  filaments.  The  upper  surface  of  this 
deposit  is  fairly  even  and  the  fibers  round  and  parallel  in  arrange- 
ment. The  inner  part  of  the  specimen  is  similar,  but  the  fibers  are 
sharper  and  resemble  blades  of  grass  arranged  loosely,  giving  an 
open  and  porous  structure.  The  under  surface  of  these  fans  is  more 
uneven,  the  fibers  are  round  and  covered  with  little  pellets  of  lime 
sometimes  clustered  in  botryoidal  forms,  while  the  threads  them- 
selves are  irregularly  arranged,  as  if  a  skein  of  silk  floating  in  the 
shifting  currents  of  a  stream  were  suddenly  turned  to  snowy  traver- 
tine. Plate  LXXXI  shows  the  upper  surface  of  a  part  of  one  of  these 
travertine  fans,  on  which  the  travertine  frost-work  is  particularly 
beautiful.  The  specimen  is  formed  of  a  stringy  or  fibrous  deposit 
covered  by  gnarled  and  knotted  ropy  forms,  whose  surface  is  cov- 
ered by  aggregated  travertine  pellets  of  varying  sizes  up  to  one- 
eighth  of  an  inch  in  diameter,  these  in  turn  coated  with  a  drusy 
frost-work  of  little  crystals.  Bubble-like  shells  of  translucent  wax- 


648  FORMATION   OF   HOT   SPRING    DEPOSITS. 

like  travertine,  sometimes  entire,  oftener  broken,  lie  between  the 
fibers  or  entangled  in  the  network,  their  broken  edges  beaded  and 
their  surface  dotted  with  minute  pellets  of  the  same  material.  An 
examination  of  a  fragment  of  this  porous  fibrous  travertine  with  a 
pocket  lens  shows  that  the  fibers,  tubes;  and  blades  are  built  up  of 
minute  rods  lying  alongside  of  one  another  and  cemented  into  bun- 
dles or  plates.  Each  rod  has  a  hard  vitreous  center,  with  an  outer 
more  opaque  coating.  Dissolving  a  little  fragment  of  the  traver- 
tine in  dilute  hydrochloric  acid  shows  that  each  little  rod  is  formed 
by  a  single  algse  thread. .  Remembering  the  occurrence  of  the  fans 
of  this  fibrous  travertine,  we  can  only  conclude  that  the  formation 
-~)  is  produced  by  the  white  species  of  algse  so  common  in  the  hotter 

wafers  of  "the  springs. 

The  curious  mushroom-shaped  forms  ^found  in  the  channels  of 
many  of  the  springs  are  detached  with  difficulty,  as  the  deposit  is 
quite  hard  when  fresh.  The  top  is  usually  wet  by  the  ripples  and 
spray  of  the  stream,  but  is  above  the  general  body  of  water.  This 
upper  surface  ^s_ jpjfled  by  a  network  of  little  ridges  one-eighth  t)f 
an  inch  high,  with  basin-like  depressions  between.  The  color  is  a 
bright  orange  red,  which  is  most  brilliant  in  the  depressions,  where 
one  familiar  with  algse  at  once  recognizes  the  vegetable  nature  of 
the  color.  A  transverse  section  of  the  specimen  proves  that  it  is 
also  of  algous  origin.  The  stem  consists  of  fibrous  travertine  re- 
sembling that  forming  the  "  fans."  This  forms  the  center  or  middle 
layer  of  the  cap  of  the  toadstool  also,  but  is  overlaid  by  a  layer  one- 
quarter  to  three-quarters  of  an  inch  thick  of  quite  different  structure. 
This  top  layer  is  also  fibrous,  but  the  fibers  are  short,  stout,  and 
perpendicular  to  the  underlying  deposit.  The  under  side  of  the  cap 
is  coated  with  hard,  porcelanous  travertine,  with  smooth  surface, 
often  dotted  with  botryoidal  clusters  of  white  pellets,  to  which 
sulphur-coated  filaments  are  often  attached.  Both  varieties  of 
fibrous  travertine  show  a  netted  mass  of  algae  filaments  when  dis- 
solved in  dilute  acid.  The  most  common  variety  of  travertine, 
forming  the  riffled  surfaces  of  the  rounded  slopes,  benches,  and  ter- 
raced basins,  is  like  that  forming  the  top  layer  of  the  mushroom 
forms  just  mentioned. 

The  riffled  surface  is  due  to  innumerable  little  ridges  which  run 
across-the  surface  in  wavy  lines,  and,  meeting,  form  miniatures  of  the 
larger  basins.  If  the  slope  is  very  gentle  these  little  basins  are  pro- 
portionately larger  and  the  dividing  walls  very  thin,  while  on  steeper 
slopes  the  ridges  are  thick  and  close  together,  producing  a  reticulated 
surface.  While  wet  by  the  hot  water  the  color  is  generally  quite 
brilliant.  If  the  volume  of  water  be  large  and  the  current  rapid, 
the  color  is  a  creamy  white,  shading  at  the  shallower  and  less  rapid 
parts  of  the  overflow  into  pale  salmon  and  pink,  and  these  to  orange, 
red,  and  burnt  sienna.  If  this  deposit  be  examined  with  a  lens  the 


U.   8.   GEOLOGICAL  SURVEY 


NINTH  ANNUAL  REPORT      PL.    LXXXI 


TRAVERTINE,  MAMMOTH  HOT  SPRINGS. 


WEED.] 


WEATHERING    OF   THE    TRAVERTINE. 


649 


color  is  seen  to  be  due  to  a  fuzzy  growth  of  algae,  and  if  a  fragment 
be  carefully  dissolved  in  dilute  hy-drochloride  the  fuzzy  coating  is 
found  to  be  only  the  tips  of  the  living  ends  of  algse  threads  buried  in 
the  deposit  beneath.  The  structure  is  fibrous  and  quite  like  the  upper 
layer  of  the  form  last  described.  Where  the  travertine  forming  the 
riffled  slopes  is  broken  down,  showing  its  general  structure,  it  is  seen 
to  consist  of  concentric  shells  or  curved  plates  of  varying  density 
and  thickness.  This  evidences  varying  conditions  of  deposition, 
such  as  changes  in  the  supply,  and  consequently  of  temperature, 
affecting  the  nature  of  the  plant  growth. 

Changes  of  structure  are  easily  produced  in  this  way,  as  the  com- 
pactness of  the  deposit  depends  largely  upon  the  rapidity  of  deposi- 
tion, being  least  where  most  quickly  formed.  Changes  may  also  be 
due  to  the  effect  of_  sudden,  cold,  O]/  the  different  seasons,  as  intense 
cold  might  Eill  the  plant  growth,  and  the  less  evaporation  of  the 
winter  months,  with  a  probable  less  vigorous  growth  of  the  algae, 
would  produce  a  thinner,  more  compact  layer  of  sinter.  In  general  it 
may  be  stated  tUatf variations  in  evaporation  and  in  the  growth  of 
the  algous  vegetation  will  produce  variations  in  the  structure  of  the 
deposit. 

Another  common  variety  is  formed  of  overlapping  layers  of  fibrous 
travertine,  resembling  a  thatched  roof ;  it  is  but  another  form  of 
that  making  the  fan-shaped  masses  and  is  produced  by  either  the 
white  or  green  filamentary  algae.  This  deposit  originates  the  pillars 
of  the  Pulpit  Basins  and  of  others  like  them. 

At  the  edges  of  the  Main  Springs  is  a  very  hard  laminated  sinter 
formed  by  the  evaporation  of  the  water  but  tinted  by  the  plant  life 
present.  The  lining  of  these  bowls  and  of  the  adjoining  pools  is 
formed  of  a  mossy  deposit  already  described. 

Coralloidal  travertine  is  found  in  many  quiet  basins  and  pools 
where  the  water  is  concentrated  by  evaporation  and  the  lime  crystal- 
lizes out  upon  the  web  of  algae  threads  present  in  the  water,  produc- 
ing very  delicate  forms  resembling  certain  species  of  corals.  Some- 
times such  deposits  support  the  pellicle  of  lime  gathering  on  the 
surface,  and  thus  the  pool  is  completely  roofed  over.  The  stems  of 
this  variety  of  tufa  are  thickly  set  with  a  drusy  coating  of  crystals 
arranged  perpendicularly  to  the  surface  of  the  stem.  The  honey- 
combed deposit  found  in  many  of  the  dry  and  empty  basins  is  formed 
by  the  rising  of  gas  bubbles  through  the  soft,  gelatinous  mass  of  the 
algsey  the  tubes  remaining  open  during  the  conversion  of  the  growth 
into  solid  travertine. 

WEATHERING  OF  THE  TRAVERTINE. 

Deprived  of  their  supply  of  water,  the  travertine  slopes  lose  their 
brilliant  colors,  which  soon  fade  out,  leaving  a  chalky  white  surface; 
this  darkens  by  prolonged  exposure  to  a  light  gray  and  in  a  few 


650  FORMATION    OF    HOT    SPRING    DEPOSITS. 

years  to  the  dull  gray  tone  of  the  older  deposits.  This  gray  tint  is 
only  a  surface  coloration,  for  the  deposit  beneath  is  still  pure  white. 

Frost  is  the  greatest  foe  to  the  preservation  of  the  basins  and  ter- 
races. In  winter  the  cool  overflow  from  the  springs,  with  rain  and 
melted  snow,  freezes  upon  the  surface  of  the  deposit,  and  thickening, 
tears  off  the  walls  of  the  terraced  basins  by  its  weight,  or  freezing  in 
the  porous  travertine  and  in  its  cracks  and  fissures,  opened  by  the 
settling  of  the  deposit,  pries  off  and  loosens  many  of  the  most  beauti- 
ful forms  of  the  tufa.  A  judicious  distribution  of  the  overflow  from 
existing  springs  would,  however,  rebuild  and  repair  many  of  the 
ruined  and  crumbling  slopes  and  basins  without  detracting  from  the 
beauty  of  other  parts  of  the  deposit. 

Infiltrating  waters  from  the  overflow  of  the  springs  carrying  carbon- 
ate of  lime,  effect  a  change  in  the  open  and  porous  tufa,  hardening  it 
into  a  denser  and  more  compact  rock.  The  travertine  is  also  altered 
by  steam  and  sulphurous  vapors  rising  through  it ;  steam  alone  often 
produces  a  coarsely  granular  structure  of  loosely  compacted  crystals. 
Where  the  vapors  are  sulphurous  the  tufa  is  converted  into  acicular 
crystals  of  gypsum,  generally  preserving  the  open  structure  of  the 
travertine,  with  sulphur  deposited  in  the  open  spaces. 

ORIGIN  OF  SILICEOUS  SINTER. 

With  the  exception  of  the  calcareous  waters  of  the  Mammoth  Hot 
Springs  already  described,  and  a  few  less  important  localities,  the  hot 
waters  of  the  Yellowstone  National  Park,  like  those  of  other  volcanic 
areas,  are  characterized  by  the  proportionately  large  amount  of  silica 
contained  in  solution.  These  springs,  like  those  of  Iceland,  may  be 
divided  into  two  groups,  of  acid  siliceous  and  of  alkaline.,  siliceous 
waters — a  distinction  quite  sufficient  for  the  purpose  of  this  article. 
The  acid  waters  include  the  Highland  springs,  those  of  Crater  Hills 
and  several  other  localities  in  the  Park,  and  are  generally  character- 
ized by  deposits  of  sulphur  and  efflorescent  alum  salts,  while  the 
waters  contain  free  hydrochloric  or  sulphuric  acids.  The  alkaline 
springs  form  the  largest  of  the  two  groups,  comprising  the  geysers 
and  the  other  hot  springs  of  the  Geyser  Basins,  and  similar  hot- 
spring  areas. 

About  these  alkaline  hot  springs  the  mineral  deposits  consist 
almost  entirely  of  silica,  partly  as  opal  in  the  clay  and  less  decom- 
posed rhyolite,  but  chiefly  as  siliceous  sinter,  a  surface  incrustation 
of  white  amorphous  silica.  This  sinter  forms  the  mounds  and  cones 
of  the  geysers  and  springs,  the  fretted  and  scalloped  rims  of  the 
quieter  pools,  and  the  great  white  flats  surrounding  the  springs. 

Although  such  deposits  of  siliceous  sinter  are  found  wherever  gey- 
ser action  is  manifested,  and  quite  commonly  in  connection  with 
alkaline  hot  springs  in  all  parts  of  the  world,  the  deposits  of  Iceland, 
New  Zealand,  and  the  Yellowstone  Park  are  much  the  best  known 


WEED.]  UPPER    BASIN    OF    FIREHOLE    RIVER.  651 

and  far  exceed  those  of  other  localities.  The  Iceland  deposits  have 
been  known  the  longest,  and  have  been  studied  by  many  observers. 
The  Haukadal  area  is  the  most  familiar,  as  it  is  here  that  the  Great 
Geyser  is  situated.  At  this  place  the  white  sinter  deposits  cover 
many  acres  of  ground  and  form  the  snow-white  basins  of  the  quietly 
boiling  springs,  and  the  mounds  of  Strokr  and  the  Geyser. 

The  New  Zealand  sinter  areas  are  similar  in  character,  but  the 
deposits  are  much  more  extensive  than  those  of  Iceland.  In  many 
parts  of  the  North  Island  there  are  sinter  flats  and  mounds  resem- 
ling  the  Iceland  and  Yellowstone  deposits,  but  in  neither  of  these 
countries  is  there  anything  to  equal  in  beauty  the  wonderful  stalactic 
basins  of  the  pink  and  white  terraces  of  Lake  Rotomahana,  which 
were  destroyed  in  the  volcanic  outbreak  of  1886.  The  sinter  deposits 
of  the  Yellowstone  National  Park  are,  however,  the  largest  known, 
covering  many  square  miles  at  the  different  geyser  basins  and  other 
hot  spring  localities.  There  is  probably  no  better  field  in  which  to 
study  the  different  varieties  of  silica  deposited  by  hot  spring  waters 
and  to  observe  the  conditions  under  which  they  are  formed.  In  the 
series  of  observations  carried  on  by  the  writer,  it  has  been  found 
that  aflarge  proportionxrf  the  siliceous  sinter  of  the  different  geyser 
basins  is  formed  by  the  agency  of  vegetable  life,  algse  and  mosses 
living  in  the  siliceous  water,  and  it  is  these  deposits  and  their  origin 
that  are  of  special  interest  in  this  part  of  the  present  paper. 

The  formation  of  siliceous  sinter  by  plant  life  has  been  found  to 
be  going  on  at  many  hot-spring  areas  in  the  Park,  in  fact  wherever 
alkaline  siliceous  waters  are  found;  but  since  it  is  necessary  to  select 
some  particular  place  where  the  details  of  such  growths  may  be  de- 
scribed, the  Upper  Geyser  Basin  of  the  Firehole  River  is  chosen,  as 
it  is  easily  accessible  and  is  seen  by  all  visitors  to  the  Park. 

UPPER  GEYSER  BASIN  OF  THE  FIREHOLE  RIVER. 
GENERAL  DESCRIPTION. 

The  Upper  Geyser  Basin  of  the  Firehole  River  lies  10  miles  west 
of  Yellowstone  Lake,  39  miles  south  of  the  north  boundary,  and  11 
miles  east  of  the  western  boundary  of  the  Park,  and  is  reached  by  a 
stage  ride  of  8  miles  from  the  Lower  Firehole,  or  of  50  miles  from 
the  Mammoth  Hot  Springs.  The  altitude  is  about  7,300  feet  above 
sea  level,  but  though  the  basin  is  quite  near  the  continental  divide 
which  separates  the  drainage  of  the  Pacific  from  that  of  the  Atlantic 
Ocean,  it  occupies  a  well-marked  depression  in  the  great  rhyolite 
plateau  of  the  Park.  Situated  almost  on  the  crest  of  the  continent, 
it  is  yet  somewhat  distant  from  the  mountain  ranges  of  the  Park, 
and  is  about  equally  removed  from  the  Gallatin  range  on  the  north, 
the  volcanic  peaks  of  the  Absarokas  on  the  east,  and  the  Teton  up- 
lift on  the  south. 


652 


FORMATION    OF   HOT    SPRING    DEPOSITS. 


The  area  of  about  two  square  miles  comprising  the  Upper  Basin,  as 
it  is  commonly  called,  has  a  fairly  level  surface,  li  miles  in  extreme 
width,  and  2£  miles  long.  This  is  inclosed  between  the  abrupt  cliffs 
of  the  Madison  Plateau  on  the  west  and  north  and  the  heavily 
wooded  slopes  of  the  continental  divide  on  the  south  and  east.  The 
rhyolite  which  forms  these  barrier  walls,  and  is  well  exposed  in  the 
cliffs  about  the  basin,  also  forms  the  floor  of  the  valley  itself,  but  is 
generally  concealed  either  by  a  sheet  of  siliceous  sinter  in  the  vicinity 
of  the  hot  springs,  or  by  its  own  ddbris,  a  black  pearlitic  sand.  The 
Firehole  River  and  its  branches,  the  Little  Firehole  and  Iron  Creek, 
drain  the  basin  ;  the  Firehole  flows  through  the  eastern  part  of  the 
area,  and  most  of  the  geysers  and  hot  springs  are  situated  upon  or 
close  to  its  banks.  Except  where  covered  by  sinter  or  hot  water 
marsh,  the  surface  is  timbered  with  a  thick  growth  of  pine  (Pinus 
Murray  ana),  and  scattering  trees  are  also  found  over  the  older,  dis- 
integrating deposits  of  sinter.  These  sinter  areas  form  the  most 


FIG.  54.  General  view  of  part  of  the  Upper  Geyser  Basin. 

striking  feature  of  the  topography  of  the  basin,  and  the  bare  white 
flats  and  sinter  mounds  are  in  strong  contrast  with  the  dark  green 
of  the  neighboring  forest.  The  mass  of  sinter  deposited  by  the  hot 
water  is  so  large  that  it  has  materially  changed  the  original  surface 
of  the  ground.  Fig.  54  shows  the  appearance  of  the  central  part  of 
the  main  geyser  area,  seen  from  the  slopes  near  the  Grand  Geyser. 


TOED.]  UPPER    BASIN    OF    FIREHOLE    RIVER.  653 

This  sinter  covering  is  variable  in  thickness,  the  maximum  depth 
being  about  thirty  feet  around  several  of  the  older  vents,  a  thickness 
which  attests  the  great  age  of  the  thermal  action.  The  sinter  sheet 
is  constantly  extending  its  boundaries,  as  shown  by  dying  and  dead 
trees  and  other  vegetation  standing  in  the  silica,  but  a  gradual  dying 
out  of  the  older  vents  permits  a  slight  surface  disintegration  of  the 
deposit,  with  a  gradual  encroachment  of  vegetation  upon  it. 

But  few  of  the  many  hundred  springs  of  the  Upper  Basin  are  tur- 
bid or  muddy,  and  the  pools  are  generally  characterized  by  the  ex- 
quisite clearness  of  the  water,  which  appears  of  varying  shades  of 
blue  or  green,  according  to  the  depth  and  amount  of  light  admitted. 
If  the  water  be  quiet,  the  transparency  is  such  that  the  minute  de- 
tails of  the  basin  can  be  seen,  even  at  depths  of  20  feet  or  more.  In 
the  quieter  springs,  where  the  temperature  does  not  exceed  150°  F., 
the  basins  are  often  lined  with  a  more  or  less  abundant  algous  growth, 
whose  orange,  red,  yellow,  brown,  and  green  tints  impart  new  shades 
to  the  water.  Though  there  are  many  of  these  laugs  the  greater 
number  of  springs  possess  a  temperature  approaching  or  equaling 
198°  F.,  the  boiling  point  at  this  altitude,  and'  in  such  springs  the 
water  is  usually  in  constant  or  intermittent  ebullition.  Around  the 
margins  of  such  springs  a  rim  of  silica  is  generally  built  up  by  the 
hot  waters.  The  inner  surface,  where  constantly  wet  by  steam  and 
spray,  is  a  bright,  tawny  yellow,  the  deposit  being  sponge-like  in  form 
and  in  color,  though  composed  of  hard  silica.  The  outer  surface  of 
these  rims  is  generally  gray,  often  ornamented  with  Dearls  or  bead- 
work  of  most  delicate  structure. 

At  the  margins  of  more  tranquil  springs  a  flat  projecting  crust  or 
edging  of  white  sinter  is  found,  sometimes  extending  out  over  the 
water  and  even  roofing  over  parts  of  the  spring,  as  shown  in  Fig.  55. 
This  edging  of  white  sinter  is  oftentimes  scalloped  in  outline,  each 
scallop  closely  resembling  fungus  growths  common  on  the  bark  of 
trees  in  damp  woods.  Many  of  the  springs  have  received  appro- 
priate names,  such  as  Sapphire  Pool,  the  Morning  Glory,  and  Chro- 
matic Spring,  but  many  more,  perhaps  equally  beautiful,  remain 
unnamed.  It  is  not  easy  to  draw  a  sharp  line  between  hot  springs 
and  geysers,  nor  is  it  at  all  necessary  ;  for  there  is  every  gradation^ 
from  a  quiet  pool  with  simple  intermittent  increase  in  temperature 
to  the  great  fountains  of  boiling  water  which  provoke  our  wonder 
and  our  admiration.  Forty-eight  geysers  are  known  in  this  basin 
each  possessing  such  peculiarities  of  eruption  or  surroundings  as  to 
make  it  of  interest  and  distinguish  it  from  its  fellows.  Most  of  these 
were  named  by  the  earlier  visitors  to  the  Park,  who  christened  the 
Giant,  Bee  Hive,  Old  Faithful,  and  other  equally  familiar  geysers. 

Even  this  brief  description  of  the  Upper  Geyser  Basin  is  incom- 
plete without  some  mention  of  the  brilliant  colors  noticed  wherever 
the  hot  waters  flow.  These  multitudinous  tints  of  red  and  yellow, 


654 


FORMATION    OF    HOT    SPRING    DEPOSITS. 


green  and  brown,  are  all  produced  by  the  growth  of  hot-water  algse, 
which,  as  I  shall  show  further  on,  eliminate  silica  from  the  hot 
waters  by  their  vital  growth,  and  contribute  largely  to  the  building 
up  of  the  sinter  deposits,  besides  giving  them  their  brilliant  tints. 


FIG.  55.  Avoca  Spring,  Upper  Geyser  Basin. 


CHARACTER  OF   THE   HOT   SPRING  WATERS. 

The  hot  waters  of  the  Upper  Basin  are  mostly  clear  and  perfectly 
transparent  and  show  in  perfection  the  blue-green  tints  of  pure 
water  in  the  many  spring  bowls  and  basins.  In  many  of  the  springs 
an  iridescent  effect  is  seen  in  the  water,  which  is  not  due  to  a  film  on 
the  surface,  but  is  caused  by  the  reflection  of  light  from  circulating 
currents.  Tested  with  litmus  paper,  the  water  is  either  neutral  or 
feebly  alkaline  in  reaction,  and  it  generally  possesses  a  slight  sul- 
phurous odor.  When  cold  it  is  flat  and  insipid  in  taste  and  scarcely 
palatable,  but  is  not  injurious.  These  alkaline-siliceous  waters  are 
similar  in  character  but  vary  slightly  in  the  amount  of  material  held 
in  solution.  Chemical  analysis  shows  this  to  consist  of  silica  and  of 
readily  soluble  alkaline  and  earthy  salts,  which  are  retained  in  solu- 
tion and  carried  off  by  the  surface  drainage,  while  a  large  part  of  the 
silica  is  deposited  about  the  springs  and  geysers. 

The  following  analyses,  made  for  the  Geological  Survey  of  the 
Park  by  Prof.  F.  A.  Gooch  and  J.  E.  Whitfield,  show  the  compost- 


WEED.] 


FORMATION    OF    SILICEOUS    SINTER. 


655 


tion  of  the  geyser  waters  of  this  basin.  Analyses  are  also  given 
of  the  water  from  the  Great  Geyser  of  Iceland,  and  from  the  New 
Zealand  geysers,  the  former  by  Damonr,1  the  latter  by  Smith.2 

Analyses  of  geyser  waters. 

[Constituents  grouped  in  probable  combination.    Grammes  per  kilogram.] 


Asta 
Spring. 

Splendid 
Geyser. 

Grand 
Geyser. 

Old 

Faithful 
Geyser. 

Great 

Geyser, 
Iceland. 

White 
Terrace 
Geyser, 
New 
Zealand. 

SiOj  silica           

.1650 

.2964 

.3035 

.3961 

.5190 

.6060 

NaCl  sodium  chloride  

.1330 

.4940 

.5643 

.6393 

.2379 

1.6220 

0048 

0140 

0218 

.0340 

*.0950 

0221 

0231 

0319 

.0478 

Trace 

.0051 

0575 

0281 

0387 

.0270 

.1342 

0335 

0350 

.0213 

0025 

.0014 

.0027 

.0279 

t.2290 

1463 

5286 

3209 

2088 

2567 

MgCO3,  magnesium  carbonate  .  . 
CaCOs  lime  carbonate    

.0035 
.0295 

.0018 

.0075 

None  .  .  . 
.0070 

.0021 
.0038 

Trace  . 
.025 

FeCOs  iron  carbonate  

.0001 

Trace... 

ALjOs  alumina       ... 

.0112 

.0051 

.0061 

.0017 

.005 

H2S  hydrogen  sulphide 

Trace 

.0002 

NHiCl  ammonium  chloride 

0002 

.0012 

Trace  .  .  . 

1045 

1989 

.0587 

KjSO4  potassium  sulphate  

.0180 

.0750 

.0091 

.0088 

Total       

6764 

1.6340 

1.3905 

1.3908 

1.2305 

2.6570 

Specific  gravity  

1.00132 

1.00108 

1.00096 

1.000205 

1.00077 

*CaCla 


tNaaO. 


FORMATION   OF   SILICEOUS  SINTER. 


The  separation  and  deposition  of  silica  from  hot  spring  waters  in 
the  form  of  siliceous  sinter  has  been  ascribed  by  different  writers  to 
one  or  more  of  the  following  causes  : 

(1)  Relief  of  pressure. 

(2)  Cooling. 

(3)  Chemical  reaction. 

(4)  Evaporation. 

At  the  Norris  Geyser  Basin  the  first  two  causes  produce  a  separa- 
tion of  silica  from  the  hot  waters,  but  the  waters  of  the  other  geyser 
basins  contain  very  much  less  silica,  and  as  far  as  observed  neither 
relief  of  pressure  nor  cooling  will  produce  a  separation  of  the  silica. 
Water  collected  from  the  springs  and  geysers  of  the  Upper  and 
Lower  Geyser  basins  was  perfectly  transparent,  and  remains  clear 

'Ann.  Chem.  u.  Pharm.,  vol.  62.  1847,  p.  49. 
2  Jour,  fur  prakt.  Chemie,  vol.  89,  1863,  p.  186. 


656  FORMATION    OF    HOT    SPRING    DEPOSITS. 

and  without  sediment  after  standing  several  years.  Experiments  in 
the  laboratory  show  that  the  silica  in  these  waters  remains  dissolved 
even  when  the  water  is  cooled  down  to  the  freezing  point,  and  it  is 
only  after  the  crystallization  of  the  water  by  freezing  that  the  silica 
is  separated  and  settled  down  as  an  insoluble  nocculent  precipitate 
upon  melting  the  ice. 

The  formation  of  sinter  by  the  waters  of  the  Iceland  geyser,  which 
analysis  shows  to  be  similar  to  the  waters  of  the  Upper  Basin  in 
character,  but  more  heavily  charged  with  silica,  is  explained  by 
Damour  *  and  Descloiseaux  by  supposing  the  silica  to  be  present  in 
solution,  as  an  alkaline  silicate,  which  is  decomposed  by  uprising 
sulphurous  and  hydrochloric  vapors  into  free  hydrated  silica  and 
alkaline  salts.  From  the  supersaturated  solution  of  silica,  formed 
in  this  way  the  silica  separates  out  in  the  form  of  sinter.  In  several 
analyses,  Damour  found  a  constant  relation  of  3  : 1  between  the  oxy- 
gen of  the  silica  and  that  of  the  bases;  when  the  alkalies  are  present 
partly  as  chlorides  and  sulphates,  formed  by  the  decomposition  of  the 
alkaline  silicates,  the  relation  existing  between  the  oxygen  of  the* 
silica  and  that  of  the  bases  of  the  undecomposed  silicates  was  found 
to  vary  from  1:5  to  1:9,  and  wherever  the  latter  proportion  pre- 
vailed, as  it  does  in  the  water  of  the  Great  Geyser,  silica  is  deposi- 
ted, the  amount  deposited  each  day  corresponding  to  the  quantity  of 
the  alkali  saturated  in  that  time  by  the  action  of  the  acid  vapors  or 
by  the  oxidation  into  sulphates  of  the  alkaline  sulphides  in  contact 
with  the  air.  Laboratary  experiments  show  that  the  waters  of  the 
Upper  Basin  remain  unaltered  upon  saturating  them  with  hydrogen 
sulphide,  and  that  the  silica  is  probably  present  in  solution  as  free 
hydrated  silica. 

LeConte  and  Rising*  suppose  the  precipitation  of  silica  taking 
place  at  Sulphur  Bank,  Cal. ,  to  be  due  to  the  neutralization  of  the 
upcoming  hot  alkaline  waters  by  descending  acid  solutions,  a  pro- 
cess evidently  not  in  operation  at  the  geysers  of  the  Upper  Basin. 

Roscoe  and  Schorlemmer  8  state  that  the  alkaline  silicates  of  the 
Iceland  waters  are  decomposed  by  the  carbonic  acid  of  the  atmos- 
phere with  a  formation  of  alkaline  carbonates  and  free  silica,  the 
latter  being  deposited.  This  gas,  passed  through  the  Upper  Basin 
waters  for  several  hours,  produced  no  visible  effect  upon  the  water. 
Bunsen,  to  whom  we  are  indebted  for  the  accepted  theory  of  geyser 
action,  ascribed  the  formation  of  the  Iceland  sinters  to  the  evapora- 
tion of  the  water. 4  His  experiments  showed  that  the  silica  of  the 
geyser  water  was  not  deposited  upon  cooling  and  only  separated  out 
upon  the  advanced  concentration  of  the  water,  but  was  readily  de- 

1  Philos.  Mag.,  London,  1847,  vol.  30,  p.  405. 

2  Am.  Jour.  Sci. ,  3d  series,  vol.  24,  p.  33. 

3  Treatise  on  Chemistry,  vol.  1,  p.  571. 

4  Pseudo-volcanic  phen.  of  Iceland:  Memoirs  of  Cav.  Soc.,  Graham,  1848,  p.  336. 


WEED.]  ALGOUS    VEGETATION    OF    THE    HOT    WATERS.  657 

posited  by  evaporation.  This  cause  produces  some  of  the  siliceous 
sinter  found  about  the  hot  springs  and  geysers  of  the  Upper  Basin, 
but  it  is  to  the  vegetation  present  in  these  hot  waters  that  we  must 
credit  the  formation  of  the  greater  part  of  the  siliceous  deposits  of 
the  geyser  basins. 

ALGOUS   VEGETATION  OF  THE   HOT   WATERS. 

Algse  are  found  in  the  thermal  waters  of  the  Upper  Geyser  Basin 
wherever  the  temperature  is  not  too  high  to  permit  their  develop- 
ment. The  limiting  degree  of  heat  at  which  they  h,ave  been  found 
is  185°  F.,  but  the  algous  filaments  are  often  found  at  that  tempera- 
ture, though  such  plants  are  immature  and  poorly  developed,  and  it 
is  not  until  the  waters  have  cooled  down  to  a  temperature  approxi- 
mating 1400  F.  that  these  growths  attain  their  full  development.  In 
these  cooler  waters  their  vegetable  nature  is  more  easily  recognizable, 
for  the  waving  green  filaments,  or  the  red  and  brown  leathery  sheets 
lining  the  springs,  closely  resemble  sea  weeds  found  on  our  coasts. 
•  But  in  the  hotter  waters  the  material  hardly  suggests  the  presence 
of  vegetable  matter,  the  densely  gelatinous  substance  resembling 
mineral  or  possible  cartilaginous  animal  material.  The  colors  of 
these  growths  are  generally  quite  brilliant,  either  golden-yellow, 
orange,  or  red,  and  in  the  hottest  waters  pale  flesh-pink,  or  even 
white.  These  algae  are  often  so  thickly  encrusted  by  silica  that  the 
plant  structure  is  not  recognizable  even  under  the  microscope,  and 
their  presence  is  often  only  to  be  distinguished  by  the  color.  It  has 
been  found  that  the  color  of  the  growth  depends  upon  the  tempera- 
ture of  the  water  so  that  differences  in  color  mark  different  degrees 
of  heat.  Some  of  the  most  striking  color  effects  of  the  Upper  Basin 
are  due  to  this  fact,  such  as  the  ribbon-like  stripes  of  overflow  chan- 
nels, and  the  concentric  rings  of  color  found  in  shallow  flaring  hot 
spring  bowls,  and  reaching  a  wonderful  development  in  the  Pris- 
matic Lake  of  the  Midway  Basin. 

The  general  sequence  of  colors  is  well  illustrated  by  the  occur- 
rence of  such  growths  in  overflow  streams  with  a  constant  volume, 
such  as  the  outlet  of  the  Black  Sand.  As  the  water  from  this  spring 
flows  along  its  channel  it  is  rapidly  chilled  by  contact  with  the  air 
and  by  evaporation,  and  is  soon  cool  enough  to  permit  the  growth 
of  the  more  rudimentary  forms  which  live  at  the  highest  tempera- 
ture. These  appear  first  in  skeins  of  delicate  white  filaments  which 
gradually  change  to  pale  flesh-pink  farther  down  stream.  As  the 
water  becomes  cooler  this  pink  becomes  deeper,  and  a  bright  orange, 
and  closely  adherent  fuzzy  growth,  rarely  filamentous,  appears  at 
the  border  of  the  stream,  and  finally  replaces  the  first-mentioned 
forms.  This  merges  into  yellowish-green  which  shades  into  a  rich 
emerald  farther  down,  this  being  the  common  color  of  fresh-water 
algae.  In  the  quiet  waters  of  the  pools  fed  by  this  stream,  the  algae 
9  GEOL 42  • 


658  FORMATION    OF    HOT   SPRING    DEPOSITS. 

present  a  different  development,  forming  leathery  sheets  of  tough 
gelatinous  material  with  coralloid  and  vase-shaped  forms  rising  to 
the  surface,  and  often  filling  up  a  large  part  of  the  pool.  Sheets  of 
brown  or  green,  kelpy  or  leathery,  also  line  the  basins  of  warm 
springs  whose  temperature  does  not  exceed  140°  F.,  but  in  springs 
having  a  higher  temperature  the  only  vegetation  present  forms  a 
velvety,  golden-yellow  fuzz  upon  the  bottom  and  sides  of  the  bowl. 
This  growth  is  rarely  noticed  in  springs  where  the  water  exceeds 
160°,  except  at  the  edge  of  the  pool.  If  the  basin  is  funnel-shaped, 
like  that  illustrated  in  Fig.  56,  with  flaring  or  saucer-shaped  ex- 
pansion, algae  grow  in  the  cooler  and  shallower  water  of  the  margin, 
forming  concentric  rings  of  yellow,  old  gold  and  orange,  shading 
into  salmon-red  and  crimson,  and  this  to  brown  at  the  border  of  the 
spring.  Around  such  springs  the  growth  at  the  margin  often  forms 
a  raised  rim  of  spongy,  stiff  jelly,  sometimes  almost  rubber-like  in 
consistency,  and  red  or  brown  in  color.  Evaporation  of  the  water 
drawn  up  to  the  top  of  such  rims  leaves  a  thin  film  of  silica,  which 
'thickens  to  a  crust  and  so  aids  in  the  production  of  a  permanent 
sinter  rim. 

Where  the  overflow  from  a  spring  spreads  out  over  the  surface  of 
a  mound  the  algse  often  grow  in  cushions  of  red,  white,  brown  or 
green  jelly,  generally  mistaken  for  simple  gelatinous  silica  colored 
with  iron,  and  indistinguishable  from  simple  mineral  material  to  the 
naked  eye,  though  the  putrid  odor  of  such  material  removed  from 
the  water  and  allowed  to  decay  indicates  its  organic  nature.  In  the 
pools  and  basins  about  most  of  the  geysers  the  bright  orange  algse 
form  a  velvety  nap  upon  the  smooth  surface  of  the  sinter.  This  is 
easily  recognizable  in  the  pools  about  the  Jewel  Geyser,  but  the 
same  growth  occurring  in  the  basins  about  Old  Faithful,  and  very 
generally  in  the  overflow  channels  of  all  the  geysers,  is  so  obscured 
by  the  silica  deposit  about  it  that  it  is  only  noticeable  because  of  its 
brilliant  color  and  the  slippery  feeling  it  imparts  to  the  surface. 

ALG^E  POOLS  AND  CHANNELS. 

The  vegetation  of  the  hot  spring  waters  attains  its  maximum  de- 
velopment in  the  self -formed  pools  and  basins  found  near  the  Emer- 
ald and  the  Black  Sand  springs  of  the  Upper  Basin  and  the  Jelly 
Spring  of  the  Lower  Geyser  Basin.  This  is  largely  because  of  the 
great  and  constant  volume  of  the  overflow  from  such  springs,  taken 
in  the  natural  water-ways  and  pools  which  the  algae  form,  and  dis- 
tributed by  a  nicely-adjusted  system,  by  which  the  continual  in- 
crease and  growth  of  different  parts  of  the  overflow  area  are  pro- 
moted and  fostered.  At  such  places  the  formation  of  sinter  by  these 
plant  growths  goes  on  rapidly,  and  the  various  gradations  may  be 
seen,  from  the  soft  jelly  to  the  firm  and  hard  sinter,  into  which  it  is 
transformed. 


WEED.]  ALG^E    POOLS    AND    CHANNELS.  659 

One  of  the  "best  places  to  observe  such  pools  is  the  flat  about  the 
EmejraMSprin^,  where  the  sinter  is  all  of  algous  origin.  The  Em- 
erald Spring,  whose  clear  green  depths  make  the  name  a  most  appro- 
priate one,  is  situated  on  the  west  bank  of  Iron  Creek,  about  three- 
fourths  of  a  mile  west  of  the  Upper  Geyser  Hotel.  The  bowl  is  36 
feet  wide,  30  feet  to  40  feet  long,  and  35  feet  deep,  surrounded  by 
a  shallow  basin  or  marginal  area  1  to  5  feet  wide,  outlined  and 
rimmed  by  a  low  border  of  firm  algous  jelly  whose  upper  surface  is 
whitened  by  silica  left  by  evaporation.  The  water  is  apparently 
perfectly  clear  and  free  from  suspended  material,  and  it  possesses  a 
temperature  of  150°  in  the  spring  bowl.  The  bottom  and  sides  of 
this  bowl  are  formed  of  a  creamy  gray  siliceous  mud,  particles  of 
which  are  probably  held  in  suspension  in  the  water.  ;  This  is  covered 
by  a  fuzzy  growth  of  light  canary-yellow  algse.  This  coloration  is 
best  seen  near  the  edge  of  the  bowl,  though  in  the  shallower  water  of 
the  margin  the  color  is  deeper,  and  in  the  recesses  where  the  tempera- 
ture is  but  135°  F.  the  growth  is  brownish-green  at  the  surface,  under- 
laid by  bright  red,  and  forms  a  soft,  leathery  sheet  on  the  bottom. 

The  overflow  of  the  spring  is  very  uniform  in  volume,  and  leaves 
the  basin  at  the  southwest  end,  running  off  in  a  channel  2  to  4  feet 
wide  and  half  an  inch  to  2  inches  deep.  This  channel  is  lined  with 
a  thin  membraneous  sheet,  whose  gamboge  yellow  shades  gradually 
into  a  yellowish  green,  with  dull  red.  and  olive  greens  at  the  borders 
of  the  stream.  Twenty  feet  from  the  outlet  the  stream  broadens 
into  an  area  of  algse  channels  and  basins,  outlined  and  dammed  up 
by  the  algous  growth.  PI.  LXXXII  shows  a  portion  of  this  area, 
photographed  after  draining  off  the  water.  In  the  foreground  is  the 
water-way,  inclosed  by  the  algous  growth  at  the  sides,  its  floor  dotted 
with  insular  masses  of  the  same  material,  the  normal  water  level 
being  up  to  their  tops.  In  the  background  is  seen  a  part  of  the  sur- 
rounding flat  with  dead  tree  trunks  standing  upright  in  the  sinter, 
their  lower  portions  white  with  silica  left  by  the  evaporation  of 
water  drawn  up  by  capillary  force.  The  algous  forms  seen  in  this 
illustration  are  quite  characteristic  of  the  growth  where  the  condi- 
tions permit  its  full  development.  This  water-way  is  floored  with  a 
sheet  of  olive  or  emerald  green,  kelpy  jelly.  Where  there  is  a  mod- 
erate current  this  lining  is  nearly  smooth,  resembling  a  sheet  of 
wet  leather,  but  in  quieter  water  this  soft  carpet  is  dotted  with  warty 
excrescences  and  little  pillars  produced  by  their  upward  growth  ;  the 
latter  sometimes  terminates  by  balloon-like  caps  or  globes  contain- 
ing a  bubble  of  gas.  When  in  the  early  stages  of  their  growth  these 
slender  spines  or  pillars  consist  of  soft  gelatinous  material,  sinking 
to  a  shapeless  mass  of  jelly  when  removed  from  the  water,  but  as 
they  increase  in  height  and  in  diameter  a  firmer  siliceous  center  is 
formed  which  gives  stability  to'  such  shapes.  When  by  their  up- 
ward growth  these  pillars  reach  the  surface  of  the  pool  they  increase 


660  FORMATION    OF    HOT    SPRING    DEPOSITS. 

rapidly  in.  diameter,  particularly  at  the  water  level,  and  a  cup- 
shaped  cap  or  crown  is  soon  formed  upon  the  pillar,  often  with  a 
vase-like  shape.  If  several  of  these  grow  near  together  the  caps  ex- 
tending laterally  soon  unite,  and  form  the  peculiar  masses  seen  in  PI. 
LXXXII.  The  continued  growth  of  new  pillars  gradually  fills  up 
parts  of  the  channel  and  eventually  pond  back  the  water,  partially  at 
first  and  at  last  entirely.  In  this  case  the  increased  depth  of  water 
resulting  permits  a  further  upward  growth  of  the  algae,  and  a  series 
of  pools  or  basins  sometimes  results,  in  which  the  water  levels  are 
quite  different,  while  the  water  cooled  in  passing  from  pool  to  pool 
possesses  different  temperatures  in  each.  A  close  view  of  such  a 
basin  is  shown  in  PI.  LXXXIII,  part  of  the  same  area  shown  in  PI. 
LXXXII.  The  algous  growth  has  here  dammed  up  a  channel  forming 
a  little  basin  already  partly  filled  with  isolated  pillars  and  aggregates 
these  growths.  The  continued  growth  of  the  algse  raises  the  water  of 
level  until  finally  the  enfeebled  current  brings  but  a  small  supply, 
with  a  consequent  gradually  lowered  temperature,  not  only  for  the 
basin  itself,  but  also  in  adjacent  pools  whose  supply  may  have  been 
entirely  cut  off.  In  such  cases,  the  nature  of  the  growth  changes ; 
it  is  not  known  that  life  ceases,  though  it  seems  probable  that  these 
algse  die,  and  new  species  are  introduced.  At  any  rate,  the  bright- 
colored  algous  jelly  forming  the  outer  covering  of  the  pillars  and 
algae  vases  changes  to  light  salmon  pink,  and  the  substance  itself 
becomes  noticeably  siliceous  or  forms  a  filmy  web  upon  the  siliceous 
center.  There  is  as  yet  no  increment  of  silica,  but  a  simple  shrink- 
ing and  hardening  of  the  gelatinous  envelope,  but  if  the  tempera- 
ture be  gradually  reduced  to  85°  F.  or  90°  F.  these  forms  become 
coated  with  a  mossy  incrustation  of  hard  silica,  and  the  algous  struc- 
ture arid  outlines  are  obscured  or  concealed  by  the  coral -like  coating. 

If  instead  of  this  gradual  reduction  of  the  volume  and  tempera- 
ture of  the  supply,  the  water  is  completely  shut  off  suddenly,  the 
gelatinous  material  dries  up,  for  the  water  in  the  basin  either  evap- 
orates or  oozes  through  the  porous  growth.  In  this  case  the  algae 
soon  lose  their  bright  colors,  which  fade  like  those  of  the  Mammoth 
Hot  Springs  to  a  delicate  salmon  pink,  and  finally  pure  white,  be- 
coming light  but  firm  structures  of  opaque  white,  hydrated  silica. 
Generally  the  pools  have  been  filled  up  by  the  pillars,  and  often- 
times completely  roofed  over  by  their  tops,  before  the  desiccation  of 
such  areas  leaves  them  a  bare  white  flat.  In  many  parts  of  the 
Upper  Basin,  the  crust  or  surface  of  the  sinter  flats  can  be  broken 
through,  exposing  a  structure  that  makes  the  origin  of  the  deposit 
at  once  apparent  to  one  familiar  with  the  algous  forms  of  hot  water 
pools. 

A  number  of  simple  experiments  were  made  with  the  overflow  of 
the  Emerald  Spring  to  determine,  first,  the  rapidity  with  which  the 
algae  establish  themselves  in  new  overflow  channels,  and  secondly, 


WEED.]  ALG.E    POOLS    AND    CHANNELS.  661 

the  effect  of  a  diminished  supply  and  of  temperature  upon  existing 
growths,  and  the  final  death  of  the  algse  when  the  water  is  completely 
shut  off.  Cutting  an  outlet  in  the  margin  of  the  spring  the  outflow 
ran  over  a  surface  of  compact,  hard  and  dry  sinter.  On  the  second 
day  this  surface  showed  a  very  faint  yellowish  coloring;  the  third 
day  this  was  easily  noticed,  and  occurred  in  patches  and  not  uniformly 
over  the  surface.  Two  weeks  later,  the  greater  part  of  the  over- 
flowed area  was  covered  with  a  fuzzy  golden-green  growth,  which 
was  coherent  and  membraneous  in  a  few  places,  but  which  as  yet 
showed  no  traces  of  the  pillars  and  related  forms  found  in  the  old 
basins.  Where  the  rim  of  the  spring  had  been  cut,  a  shallow  recess 
had  permitted  a  partial  cooling  of  the  water,  and  an  olive-colored, 
leathery  sheet  covered  the  floor.  The  current  resulting  from  the 
overflow,  immediately  raised  the  temperature  above  this  growth,, 
which  soon  looked  blistered  and  pale,  and  changed  in  the  course  of 
a  few  days  to  pale,  yellowish  green.  Reducing  the  supply  of  the  algse 
channel  and  pools  (PI.  LXXXII.)  caused  no  change  in  the  growth 
still  covered  by  the  water,  in  the  first  two  days,  but  that  portion  of 
the  growth  left  exposed  to  the  sun  soon  began  to  dry  and  shrink.  In 
twenty-four  hours  the  dark  emerald  green  of  the  leathery  sheets  had 
changed  to  dark  purple,  and  where  driest  to  black  with  a  shining 
metallic  luster.  In  drying,  the  siliceous  jelly  shrank  considerably, 
and  in  consequence  the  surface  layers  had  curled  up  in  irregular 
patches,  exposing  the  underlying  layers  of  crimson  jelly.  No  odor 
was  yet  perceptible,  but  flies  gathered  thickly  upon  many  parts  of 
the  decomposing  vegetation.  In  those  pools,  where  growth  had  pre- 
viously ceased,  the  algous  forms  were  rapidly  drying,  the  pink  tint 
fading,  and  the  more  delicate  parts  already  white  and  dry. 

On  the  third  day  the  surface  layer  of  the  leathery  sheets  was  still 
more  cracked  up,  the  patches  curled,  with  their  edges  white  and  dry, 
the  underlying  red  jelly  drying  to  rose  pink,  while  the  odor  of  decay- 
ing organic  matter  was  strong  and  repulsive.  The  lowered  temper- 
ature of  the  water  had  now  effected  the  growth  beneath  it,  and  the 
olive  and  green  flow  showed  patches  of  reddish  brown,  pink,  and 
deep  green.  The  supply  of  water  being  restored  to  portions  of  the 
water-way,  the  growth  did  not  recover  as  rapidly  as  was  expected. 
The  lustrous  black  of  the  decaying  vegetation  changed  in  the  course 
of  a  few  days  to  spotted  purple  patches,  but  the  red  layers,  still  ex- 
posed, changed  to  salmon.  There  is  no  doubt  that  if  the  water  sup- 
ply had  not  been  restored  the  colors  would  have  gradually  faded 
out,  leaving  a  white  area  of  siliceous  material  as  light  as  cork,  where 
formed  from  the  soft  and  jelly-like  algae,  but  heavier  and  denser, 
where  the  older  forms  had  grown,  this  being  the  result  at  other 
places  where  similar  pools  are  found. 

If  specimens  of  the  different  varieties  of  the  growth  be  removed 
from  the  water  and  allowed  to  dry  rapidly,  the  jelly  contracts  greatly 


662  FORMATION    OF    HOT    SPRING    DEPOSITS. 

in  drying,  the  air-dried  material  being  about  one-third  the  bulk  of 
the  moist  jelly.  The  gelatinous  coating  of  the  pillar  and  vase-shaped 
forms  curls  up  in  thin  flakes,  whose  outer  surface  retains  the  color  of 
the  growth,  exposing  the  light  flesh-colored  siliceous  frame-work  of 
the  algse. 

The  tendency  of  the  algous  growths  to  form  terraced  basins  is 
beautifully  illustrated  in  the  basins  supplied  by  the  waters  of  the 
Jelly  Springs  at  the  base  of  the  mound  of  the  Fountain  Geyser.  In 
these  basins  the  different  stages  of  sinter  forming  are  sharply  drawn, 
from  the  soft  and  brightly  colored  jelly  to  a  hard  and  stony  sinter. 

PI.  LXXXI V  shows  the  uppermost  of  these  basins ;  the  dam  pond- 
ing back  the  water  is  about  a  foot  high,  and  is  formed  of  a  fibrous  sin- 
ter, hard  and  stony  below,  but  grading  into  a  softer  material  of  cheesy 
consistency  above,  passing  into  red  and  green  algous  jelly.  The 
algse  of  this  pool  or  basin  are  brightly  colored,  and  the  forms  resem- 
ble those  of  the  Emerald  Spring,  but  the  pillars  are  taller,  owing  to 
the  greater  depth  of  the  water. 

In  a  lower  basin,  shown  in  PI.  LXXXV,  the  water  is  nearly  cold,  *• 
and  though  the  forms  are  the  same  as  those  found  in  the  basin  above 
there  is  no  trace  of  the  red,  yellow,  and  green  algous  jelly.  A  close 
view  of  the  forms  found  in  this  basin  is  given  in  the  cut  (Fig.  56). 
In  the  basin,  while  covered  by  water,  these  peculiar  structures  are 
light  pink,  but  they  become  white  upon  drying.  The  tops  of  the 
forms  shown  in  the  illustration  are  margined  and  capped  by  a  very 
thin  film  of  silica  left  by  evaporation,  and  the  small  share  which  that 
agent  takes  in  the  formation  of  these  deposits  is  shown  in  the  rela- 
tive proportion  of  this  edging  to  the  mass  of  pillars. 

PI.  LXXXVII  shows  two  of  the  forms  from  the  basin  figured  in  PI. 
LXXXV.  Fig.  1  is  one  of  the  finger-like  pillars,  which  do  not  reach 
to  the  surface  of  the  water.  The  specimen  is  six  inches  high  and  an 
inch  in  least  diameter.  The  pure  white  surface  is  lined  by  little 
knife-edge  ridges  and  dotted  with  spiny  points  of  silica,  all  hung  with 
small  patches  or  shreds  of  a  delicate  web  or  film  of  silica,  the  remains 
of  the  algous  jelly  that  once  covered  the  surface.  A  transverse  sec- 
tion shows  the  specimen  to  consist  of  a  central  core  of  white  siliceous 
layers  in  the  form  of  very  thin  concentric  sheets  or  cylinders,  sur- 
rounded by  a  loose  wrapping  of  similiar  paper-like  sheets.  The  outer 
surface  is  hard,  but  brittle  and  easily  broken.  Such  finger-forms 
frequently  occur  in  clusters,  sometimes  of  very  different  heights, 
and  several  often  coalesce  as  they  grow  upward,  and  produce  little 
pinnacled  shapes.  As  already  stated,  in  describing  the  algae  of  the 
Emerald  Spring,  these  pillars  continue  their  upward  growth  when 
the  algse  are  living  until  their  tops  reach  the  water  level,  when,  if 
the  plant  growth  continues,  a  spreading  top  is  formed,  upon  which 
evaporation  leaves  thin  films  of  pearly  silica. 

One  of  the  smallest  of  these  curious,  stony  yet  vegetable  forms,  is 


WEED.] 


ALG^E    POOLS    AND    CHANNELS. 


663 


shown  in  Fig.  2,  PI.  LXXX  VII.  The  specimen  figured  is  eight  inches 
high,  and  shows  in  its  graceful  curves  the  bending  of  the  original 
gelatinous  material  before  the  current  of  the  basin.  The  broader 
base  of  the  specimen  is  made  of  smaller  spiny  forms  growing  to- 
gether and  united  to  the  base  of  the  pillar.  Above  the  middle  the 
column  expands  into  a  hoop-shaped  mass,  crowned  by  irregular  bands 
of  pearly  sinter.  This  specimen  is  also  lined  by  the  little  ridges  so 
prominent  in  the  first  figure,  though  they  are  much  less  noticeable 
and  scarcely  show  on  some  parts  of  the  specimen.  Such  forms  re- 
veal quite  clearly  their  algous  origin,  but  the  stony  masses  found  in  a 
lower  and  empty  basin,  shown  in  PL  LXXXVI,  are  apparently  quite 
different  in  nature,  though  formed  by  the  incrustation  of  the  shapes 
shown  in  Fig.  56.  This  basin  is  the  lowest  of  the  series,  and  if  some 


FIG.  56.  Algae  forms,  Lower  Geyser  Basin. 


664  FORMATION    OF    HOT    SPRING    DEPOSITS. 

cause  had  not  operated  to  produce  the  death  of  the  algae,  and  an  incrus- 
tation of  the  structures,  before  the  filling  up  of  the  basin  with  their 
siliceous  stems,  the  basin  would  now  form  only  a  bench,  indistinguish- 
able from  the  rest  of  the  sinter  flat  above  it.  Fig.  3,  PL  LXXXVII, 
shows  a  specimen  taken  from  this  basin ;  the  transverse  section  proves 
it  to  consist  of  a  central  form  similar  to  Fig.  2,  PL  LXXXVII,  covered 
with  a  mossy  coating  of  silica,  three-fourths  of  an  inch  thick,  which 
rounds  off  and  hides  the  outlines  of  the  incrusted  pillar.  This  coating 
has  a  rough  coral-like  surface,  with  clustered  knobs  of  silica,  which 
a  lens  shows  to  consist  of  delicate  spicules  of  glassy  sinter.  The 
deposit  is  firm  and  hard,  and  the  aggregated  masses  form  a  compact 
and  solid  sinter. 

In  the  pools  supplied  by  the  Black  Sand  Spring,  which  are  collect- 
ively known  as  Specimen  Lake,  the  algae  are  exactly  like  those  de- 
scribed, save  that  they  are  generally  slimmer  and  taller,  often  twelve 
or  fifteen  inches  in  length,  and  their  tops,  uniting,  form  a  solid  roof, 
often  in  turn  the  floor  of  a  new  basin,  with  a  new  growth  of  algae.  The 
pillars  rarely  grow  solidly  and  closely  together,  so  that  specimens  of 
the  sinter  are  coral-like,  the  pillars  coated  with  an  efflorescent  gran* 
ular  coating  of  silica.  The  desiccation  of  such  areas  leaves  a  deposit 
of  sinter  whose  surface  shows  no  trace  of  its  origin  and  of  the  beau- 
tiful forms  beneath,  and  such  deposits  occur  in  many  places  about 
the  Geyser  Basin. 

The  exact  manner  in  which  the  algse  of  these  waters  eliminate  the 
silica  from  solution  is  not  known,  but  the  process  appears  to  be  due 
to  the  vital  growth  of  the  plant,  for  both  the  algse  filaments  and  their 
slimy  envelope  are  formed  of  gelatinous  silica.  Upon  the  death  of 
the  algae  which  have  separated  this  jelly  from  the  spring  waters,  there 
is  a  loss  of  a  large  part  of  it§  water,  and  a  change  to  a  soft,  cheesy, 
but  more  permanent  form.  This  dehydration  is  carried  still  farther 
if  the  silica  be  removed  from  the  water  and  dried,  but  if  allowed  to 
remain  in  the  cold  water  pools  there  is  a  further  separation  of  silica, 
possibly  due  to  organic  acids,  formed  by  the  decaying  vegetation 
reacting  upon  the  silica  salts  of  the  water ;  this  hardens  the  existing 
structures,  in  certain  cases,  and  generally  covers  the  pillars  with  a 
frost-like  coating  of  silica. 

In  general,  it  may  be  stated  that  the  large  vase  and  pillar  forms 
found  in  the  algae  pools  can  be  produced  only  by  a  concurrent  life 
and  death  of  these  plants,  the  outer  layers  continually  growing,  the 
innermost  dying.  This  is  readily  seen  to  be  the  cause  of  the  peculiar 
structure  of  these  forms.  The  central  core  is  a  pillar,  sometimes 
hollow,  sometimes  solid,  consisting  of  exceedingly  thin  superimposed 
layers  of  silica,  each  of  which  corresponds  to  a  layer  of  algae  jelly, 
which  has  become  hardened  by  the  death  of  the  plants  and  the  loss 
of  water.  The  column  increases  in  diameter  by  the  growth  of  the 
algae  at  the  surface,  and  a  simultaneous  death  and  hardening  of  the 


WEED.]  FIBROUS   VAEIETIES    OF    ALC40US    SINTER.  665 

inner  layer  of  jelly.  The  algous  envelope  consists  of  two,  three,  or 
more  thin  membraneous  layers,  the  outer,  green,  the  inner,  tomato 
red,  these  layers  corresponding  to  the  laminae  of  the  hardened  inner 
core.  The  slimy,  leathery  sheets,  so  common  in  the  cooler  springs 
(100°  F.  to  135°  F.),  are  similar  in  nature,  and  when  dried  are  thin 
crusts  of  light,  corky  sinter.  Another  form,  abundant  about  the 
Solitary  Spring,  where  it  has  bujjt  up  a  sinter  mound  of  considerable 
magnitude,  consists  of  cushion-like  masses  of  jelly,  sometimes  six 
inches  thick,  which,  if  removed  and  dried,  shrivel  up  to  less  than 
half  that  thickness,  and  are  exceedingly  light  and  porous,  floating 
on  water.  The  under  layer  of  such  thick  masses  is  decaying  and 
changing  to  sinter,  into  which  it  can  be  traced  in  situ. 

FIBROUS   VARIETIES   OF  ALGOUS  SINTER. 

Besides  the  varieties  of  sinter  formed  by  these  vegetable  jellies, 
there  are  two  kinds  of  fibrous  sinter,  very  abundant  about  some  of 
the  hot  springs,  and  constituting  an  important  part  of  the  sinter 
deposits.  The  first,  forming  in  the  overflow  channels  of  many  of  the 
geysers  of  the  Upper  Basin,  is  finely  fibrous,  consisting  of  layers  one- 
sixteenth  of  an  inch  to  half  an  inch  thick,  each  stratum  resembling 
a  very  fine  thick  white  fur.  This  sinter  is  formed  by  the  growth  of 
the  little  algae — Calothrix  gypsophila  Kg. —or  the  young  form,  Mas- 
tigonema  thermale,  the  latter  olive-colored  and  forming  the  sinter 
alluded  to  later  in  the  section  of  the  sinter  walls  of  the  crater  of  the 
Excelsior  Geyser.  The  second  form  is  fibrous,  and  occurs  in  rough, 
straw-like  masses,  with  thatched  arrangement.  A  coarse  variety  is 
due  to  a  bright  red  species  of  algae — Leptotlirix — a  finer  variety  to 
Leptofhrix  (or  Hypheothrix)  laminosa,  a  species  found  from  135° 
to  185°  F.,  and  ranging  in  color  from  white  to  flesh,pink,  yellow,  and 
red  to  green,  as  the  water  cools.  The  specimens  determined  came 
from  the  mounds  of  Sentinel  Creek. 

The  proportion  of  algous  sinter  forming  the  deposits  about  the 
Geyser  Basins  is  strikingly  shown  in  the  following  section  of  the 
strata  forming  the  wall  of  the  Excelsior  crater  :  , 

Inches. 

21.  Uppermost  layer,  fibrous,  "  furry"  sinter 15 

20.  Cemented,  sinter  fragments 0. 5 

19.  Fibrous  sinter,  brownish  colored 3 

18.  Thatch-like,  fibrous  sinter 0.5 

17.  Cemented  fragments 3 

16.  Thatch-like  sinter 3 

15.  Fibrous    2 

14.  Cemented  fragments 1 

13.  Thatch-like 12 

12.  Same,  mixed  with  cemented  material  of  same  nature 2 

11.  Fibrous,  9  layers  J  inch  to  1  inch  thick 6 

10.  Cemented  fragments,  partly  of  organic  origin 6 

9.  Fibrous. .  2 


666  FORMATION    OF    HOT    SPRING    DEPOSITS. 

Inches. 

8.  Flaky  sinter  formed  by  algous  sheets 4 

7.  Fibrous  and  thatch-like,  about  equally  divided 36 

6.  Fibrous 2 

5.  Flaky,  pearly,  algous 3 

4.  Thatch-like,  brown 10 

3.  Fibrous,  10  to  20  layers 8 

2.  Cemented  material 8 

1.  Fibrous..  12 


11  ft.,  6  ins. 

In  this  section  fifty  per  cent,  consists  of  the  fibrous  sinter  formed 
by  Mastigonema,  36  per  cent;  (4  feet,  2  inches)  of  the  thatch-like  or 
flaky  sinter  formed  by  the  membranous  alga?,  Leptothrix . 

The  crater  wall  nearest  the  Prismatic  Spring  is  15  feet  high,  and 
the  sinter  may  be  thicker,  as  the  underlying  material  is  not  exposed. 
This  sinter,  which  forms  a  plateau  covering  many  acres,  has  been 
formed  by  the  vegetation  nourished  by  the  overflow  from  the  Pris- 
matic Spring,  and  the  older  layers  have  a  terraced  surface  exactly 
like  that  of  the  deposit  now  forming  about  this  spring.  , 

RATE   OF  DEPOSITION  OF  SILICEOUS  SINTER. 

The  pearl-beaded,  coralloid  forms  of  sinter  found  about  spouting 
vents  are  formed  very  slowly.  In  one  case,  where  the  signatures  of 
a  party  who  visited  the  geysers  in  1879  are  known  to  be  authentic, 
the  pencil  marks  are  covered  by  a  glaze  of  silica  but  T^7  of  an  inch 
thick,  or  an  increase  of  ToV<j  of  an  inch  a  year,  and  this  where  the 
conditions  for  the  formation  of  sinter  by  evaporation  are  quite  favor- 
able. 

The  difference  between  the  rate  of  deposition  of  geyserite  by  these 
waters  and  those  of  the  Norris  Basin,  notably  by  the  water  of  the 
Opal  Springs  Coral,  is  shown  by  the  fact  that  at  the  Opal  Spring  an 
incrustation  of  one-quarter  of  an  inch  formed  in  three  weeks. 

Other  names,  written  upon  the  salmon-colored  channels  running 
into  the  Firehole,  near  the  Castle  and  Saw-Mill  geysers,  show  a 
growth  of  2  o~o  of  an  inch  to  -^  of  an  inch  a  year,  but  this  rate  is 
effected  by  the  combination  of  very  favorable  conditions  for  evapora- 
tion and  the  presence  of  algae. 

The  fibrous  sinters  forming  the  flow  of  the  geyser  channel  are 
composed  of  layers  from  ^0-  to  TO  of  an  inch  thick  and  averaging  -£o 
of  an  inch.  If  they  represent  a  year's  growth,  and  the  evidence 
favors  that  view,  the  line  of  glassy  silica  separating  them  being 
formed  during  the  winter,  then  the  rate  is  -*fa  of  an  inch  a  year. 

On  the  other  hand,  the  thick  masses  of  jelly  found  in  some  of  the 
overflow  areas  may  form  sinter  with  comparative  rapidity.  Thus 
the  channel  of  the  Beauty  Spring,  which  contained  no  water  in  1887, 
was  filled  with  a  growth  of  vegetable  jelly  5  inches  thick  in  1888, 


WEED.]  MOSS    SINTER.  667 

nourished  by  the  largely  augmented  overflow  of  the  spring.  A  mass 
of  this  was  cut  out  when  the  place  was  visited  in  July,  and  upon  the 
sinter  a  new  growth  1£  to  li  inches  thick  had  formed  by  October, 
seventy -three  days'  growth,  while  areas  of  what  had  been  bright 
colored  jelly  in  July  had  diverted  the  water  by  their  growth,  and 
were  now  hardened  and  pink,  and  rapidly  passing  into  firm  and  solid 
sinter. 

MICROSCOPIC   EVIDENCE. 

A  microscopic  examination  of  specimens  collected  at  the  Beryl 
Spring,  Gibbon  canyon,  shows  that  the  fibrous,  asbestos-like  mate- 
rial consists  of  minute  tubes  of  glassy  transparent  silica  correspond- 
ing to  the  filaments  of  the  growing  algse.  In  this  case  the  filaments 
appear  to  have  been  free  from  the  enveloping  jelly,  which  dries  to 
an  opaque  white  silica  and  hides  the  filaments  and  rods  of  most 
growths. 

Thin  sections  of  siliceous  sinters  fail  to  show  the  origin  and  nature 
of  the  deposit  as  clearly  as  had  been  hoped.  A  section  of  *  dried 
algous  jelly  from  the  Emerald  Spring  shows  innumerable  interlaced 
and  interwoven  filaments,  with  some  glassy  silica  between.  A  hard 
fibrous  sinter,  formed  by  the  long  filamentary  growth  of  an  overflow 
channel,  shows  only  traces  of  the  algae  filaments  under  the  micro- 
scope, but  consists  very  largely  of  minute  globules  of  glassy  silica, 
varying  somewhat  in  size  and  corresponding  to  those  forming  the 
cells  of  the  algse.  These  are  held  together  in  a  cementing  matrix  of 
glassy  amorphous  silica.  Thin  sections  of  a  sinter  formed  of  broken 
fragments  of  algse  pillars,  cemented  into  a  firm  hard  sinter,  shows  a 
similar  structure. 

If  many  of  the  algous  sinters  fail  to  reveal  an  organic  structure 
beneath  the  microscope,  they  are  nevertheless  easily  distinguished 
from  the  more  glassy_an_dj3early  sinters  formed  by  evaporation.  A 
thin  section  of  a  sinter  from  the  Solitary  Spring,  Upper  Basin,  shows 
in  marked  contrast  the  numerous  and  extremely  thin  overlapping 
layers  of  lustrous  pearl  sinter  formed  by  evaporation  and  the  duller 
chalky  white  of  the  algous  formation. 

MOSS   SINTER. 

Besides  the  deposits  of  siliceous  sinter  formed  by  the  algous  vege- 
tation of  the  hot  waters,  extensive  deposits  of  sinter  are  found  on 
the  slopes  below  the  Hillside  Springs,  which  are  due  to  the  growth 
of  mosses.  These  springs  issue  from  the  rhyolite  slopes  beneath  the 
cliffs  of  the  Madison  Plateau,  and  the  waters,  whose  temperature  is 
184°  to  198°  F.,  contain  both  silica  and  lime  in  solution,  which  they 
deposit  in  their  downward  flow.  On  the  lower  part  of  the  slopes 
the  water  is  cooled  to  blood  heat,  and  has  lost  much  of  its  lime  and 
part  of  its  silica.  This  part  of  the  slope  is  terraced  with  basins  sug- 


668  FORMATION    OF    HOT    SPRING    DEPOSITS. 

gesting  those  of  the  Mammoth  Hot  Springs,  but  covered  with  a  bright 
green  growth  of  moss.  These  basins  are  formed  of  a  porous  yellow 
sinter,  full  of  moss  stems,  and  o'ften  consisting  entirely  of  these 
plant  structures. 

Chemical  analysis  shows  this  substance  to  be  a  true  siliceous  sinter 
(see  analysis,  p.  670).  This  sinter  is  not  formed  by  evaporation,  nor 
by  any  of  the  causes  discussed  in  considering  the  precipitation  of 
silica  from  solution,  but  it  is  due  to  the  abstraction  of  silica  from  the 
water  by  the  mosses  covering  the  surface  of  the  basins.  This  moss 
has  been  determined  by  Prof.  Charles  K.  Barnes,  of  the  University 
of  Wisconsin,  to  be  Hypnum  aduncum  var.  graftilescens  Br.  &  Sch. 

DIATOM  BEDS. 

Besides  the  elimination  of  silica  from  the  hot-spring  waters  by  the 
algous  growths  living  in  them  and  by  the  mosses  of  the  cooled  water, 
there  is  a  further  secretion  of  that  substance  by  several  species  of  di- 
atoms which  live  in  the  tepid  waters  of  the  hot-spring  marshes,  and, 
though  they  do  not  form  siliceous  sinter,  their  remains  accumulate 
as  beds  of  diatom  earth  that  are  often  of  great  thickness  and  width. 

It  is  well  known  that  the  single-celled  algae,  called  diatoms,  pos- 
sess in  a  remarkable  degree  the  power  of  separating  silica  from  solu- 
tion to  form  the  beautifully  marked  siliceous  armor  of  the  plant. 
In  the  ocean  waters  this  action  is  the  more  remarkable  because  of 
the  exceedingly  small  proportion  of  silica  found  in  solution  in  the 
water,  and  the  almost  incredible  activity  necessary  on  the  part  of 
the  plant  to  secure  an  adequate  supply.  As  the  silica  of  such  dilute 
waters  is  not  separable  by  any  known  chemical  process,  its  elimina- 
tion must  needs  be  credited  to  some  vital  process  of  the  plant 
growth,  and  it  is  this  action  which  gives  to  this  low  form  of  life  its 
importance  as  a  geological  agent.  As  the  Diatomacecz  exist  under 
very  diverse  and  extreme  conditions  of  environment,  occurring  in. 
nearly  every  country  pond  and  stream,  as  well  as  the  icy  waters  of 
Polar  seas,  the  heated  currents  of  the  tropic's,  and  even  the  almost 
boiling  waters  of  hot  springs,  we  are  not  surprised  to  find  them  ex- 
isting also  in  the  siliceous  waters  of  the  Yellowstone  Springs,  which, 
indeed,  seem  peculiarly  adapted  to  the  needs  and  growth  of  these 
little  plants.  Investigation  shows,  however,  that  while  diatoms 
occur  in  the  ponds  of  the  hot-water  algae,  whose  occurrence  has 
already  been  described  in  detail,  yet  they  are  only  found  in  abund- 
ance in  the  cooled,  tepid  waters  of  the  springs.  In  such  waters  they 
are  exceedingly  abundant,  and  form  the  ooze  of  which  the  marshes 
of  the  geyser  basins  are  so  largely  composed. 

A  typical  marsh  of  this  character  is  found  near  the  beautiful 

^  Emerald  Springs  of  the  Upper  Geyser  Basin.     A  large  part  of  this 

marsh  is  covered  with  a  sparse  growth  of  rushes  and  brackish-water 

vegetation,  which  of  course  is  gradually  filling  it  up  and  convert- 


WEED.]  NATURE    OF    SILICEOUS    SINTER.  669 

ing  the  bog  into  a  fairly  firm,  grass-grown  meadow  bottom.  But 
the  greater  area  is  at  present  quite  wet,  and  its  treacherous  ooze  and 
apparently  bottomless  depths  will  be  long  remembered  by  those  who 
have  ever  tried  to  cross  the  marsh. 

The  waters  of  this  area  have  in  times  past  encroached  upon  the 
neighboring  patch  of  timber,  killing  the  trees,  whose  bare  gray 
trunks  stand  upright  in  the  ooze  or  lie  scattered  about  and  half  im- 
mersed beneath  the  surface.  A  subsequent  partial  recession  of  the 
water  has  left  a  bare  white  strip  between  bog  and  woods,  on  which 
vegetation  has  as  yet  a  precarious  foothold,  and  the  gaunt,  bare  poles 
of  the  dead  pines  rise  up  from  a  barren,  powdery,  white  soil,  evi- 
dently a  dried  portion  of  the  marsh  mud.  The  semi-liquid  ooze  of 
which  the  marsh  consists  proved  upon  examination  under  the  micro- 
scope to  be  composed  of  the  beautiful  siliceous  tests  of  various 
species  of  these  minute  plants.  Samples  of  this  material,  which  Dr. 
Francis  Wolle,  of  Bethlehem,  Pa.,  has  kindly  examined  for  me,  were 
found  to  contain  the  following  species  : 


Denticula  valida  Ped. 

D.  elegans. 

Navicula  major  and  N.  viridis. 

Epitheraia  (three  species). 


Achran  these. 
Cpcconema. 
Fragilaria. 
Eurotia. 


The  first-named  species,  Denticula  valida,  formed  the  bulk  of  the 
specimen,  and  also  of  the  white  pulverulent  material  at  the  margin 
of  the  bog,  which  microscopic  examination  showed  to  be  the  dried 
remains  of  the  same  diatoms.  Samples  from  many  other  marshes  of 
this  character  were  examined  and  found  to  be  formed  of  the  same 
species. 

The  extensive  meadows  of  the  Lower  Geyser  Basin,  the  Norris 
Basin,  Geyser  Creek,  and  many  other  places  are  underlaid  by  beds 
of  diatom  earth  composed  of  these  same  species,  and  where  the 
wagon-road  crosses  these  areas  the  ditches  made  alongside  the  road 
for  drainage  exposed  the  beds,  while  square  blocks  of  the  dried  diatom 
earth  lie  scattered  about  at  the  side  of  the  road.  These  and  similar 
meadows  are  many  square  miles  in  extent,  and  the  diatom  beds  are 
often  two  to  three,  and  sometimes  six  to  seven  feet  thick.  Not  sel- 
dom the  meadows  and  diatom  marshes  overlie  ancient  hot-spring 
areas,  the  sinter  flats  and  even  the  hot  spring  mounds  and  cones 
being  completely  covered  and  hidden  by  the  covering  of  diatom 
ooze. 

NATURE  OF  SILICEOUS   SINTER. 

Siliceous  sinter,  the  siliceous  deposit  of  thermal  waters,  is  a  variety 
of  opal,  occurring  as  a  grayish  white,  or  brownish  incrustation 
about  hot  springs.  Slightly  different  varieties  have  been  described 
under  different  names  :  a  pearly  lustered  specimen  from  Santa  Fiora, 
Italy,  being  called  Fiorite  by  Thompson;  a  filamentary  sinter  from 


670 


FORMATION    OF    HOT    SPRING    DEPOSITS. 


St.  Michael,  Azores,  described  as  Michaelite;  while  the  Iceland  and 
New  Zealand  sinters  are  known  as  geyserite. 

Siliceous  sinter  varies  much  in  appearance  and  in  structure,  accord- 
ing to  its  manner  of  formation ;  it  is  sometimes  earthy  and  crumbly, 
often  finely  laminated  and  shaly  or  light  and  porous,  occasionally 
fibrous  or  even  filamentous,  and  rarely  compact  and  flinty.  It  is 
generally  opaque,  though  often  possessing  a  vitreous  luster,  and 
rarely  translucent,  and  it  grades  into  hydrophane  and  hyalite  by 
alteration.  The  tyCtryoidal  and  coralloidal  forms  are  generally  found 
only  about  the  mouth  of  geysers  and  steam  vents,  and  are  usually 
more  compact  and  translucent  than  other  varieties.  The  sinters  pro- 
duced by  algse  are  generally  very  light,  with  an  open,  porous,  almost 
cavernous  structure,  but  this  is  often  altered  to  hard  opal  sinter  by 
infiltering  water.  The  following  table  shows  the  composition  of  a 
number  of  Yellowstone  sinters,  with  the  analyses  of  Michaelite  and 
the  Iceland  and  New  Zealand  geyserites  added  for  comparison: 

• 

Analyses  of  Yellowstone  sinters. 


I. 

II. 

III. 

IV. 

V. 

VI. 

VII. 

VIH. 

IX. 

X. 

SiOa,  silica     

89.54 

81.95 

93.88 

93.37 

89.72 

87.67 

82.29 

86.03 

92.67 

A14O3,  alumina  
FeO,  ferrous  oxide  .  . 
CaO  lime 

2.12 
Trace. 
1  71 

6.49 
Trace  . 
0  56 

1.73 
0.14 
0  25 

1.16 
Trace  . 
0  29 

j-   1.02 
2  01 

0.71 
0  40 

(,     1.36 
(  Trace  . 

!-    1.21 
0.45 

0.80 
0.14 

j  • 
1  .. 

Trace 

0  15 

0  07 

0  05 

Trace 

0  40 

0.05 

NaaO,  soda   

1.12 

2.56 

0.28 

0.11 

0.82 

i 

(   0.18 

KjO,  potash 

0.30 

0.65 

0.23 

0.02 

Trace 

j-   0.38 

\ 
\   0.75 

SOj  sulph  acid 

Trace 

0.16 

0.20 

0.31 

Trace  . 

Cl  chlorine 

Trace 

Trace 

NaCl  sodic  chloride 

0  18 

0  08 

1  50 

HjO,  water  

5.13 

7.50 

3  37 

4.17 

10.40 

16.35 

11.52 

5.45 

Total 

99  92 

100  02 

100  33 

100  41 

100  09 

100  00 

100  00 

99.99 

100.04 

No.  I,  is  a  compact  white  sinter  from  the  mound  of  Old  Faithful. 

No.  II,  is  a  grayish  sinter  from  the  margin  of  Splendid  Geyser. 

No.  Ill  is  a  light  porous  algous  sinter  from  Solitary  Spring. 

No.  IV  is  the  analysis  of  a  dried  specimen  of  jelly  from  Emerald 
Spring. 

No.  V  is  the  moss-sinter  from  Asta  Spring,  Hillside  Group. 

These  analyses  were  all  made  by  Mr.  J.  E.  Whitfield  for  the 
Geological  Survey  of  the  Yellowstone  National  Park. 

No.  VI  is  the  analysis  of  Michaelite  from  the  Azores,  by  Webster.1 

No.  VII  is  a  geyserite  from  the  mound  of  the  Great  Geyser  of  Ice- 
and,4  by  Damour. 

'Webster,  Am.  Jour.  Sci.,  1st  series,  1821,  vol.  3. 

*  Bull.  Soc.  Geol.  de  France,  3d  series,  1848,  vol.  5,  p.  160. 


WEED.]  NATURE    OF    SILICEOUS    SINTER.  671 

No.  VIII  is  a  hard  white  sinter  from  the  White  Terrace,  New 
Zealand,  Mayer.1 

No.  IX  is  a  white  sinter  from  Steamboat  Springs,  Nevada,  ana- 
lyzed by  Woodward.2 

Analysis  No.  I  shows  the  composition  of  a  sinter  in  which  evapo- 
ration and  algous  growth  both  cause  the  separation  of  the  silica. 
The  sinter  from  the  Splendid  Geyser,  whose  analysis  is  given  in  No. 
II,  is  a  deposit  formed  without  the  aid  or  presence  of  plant  life, 
wholly  by  the  evaporation  of  the  geyser  water.  The  interior  of  the 
specimen  is  composed  of  irregular  crinkled  laminae  of  greenish  gray 
sinter,  some  of  it  possessing  a  nacreous  lustre ;  this  is  covered  by 
light  gray  fibrous  sinter,  the  fibers  short  and  perpendicular  to  the 
surface,  and  resulting  from  the  growth  of  little  spicules.  The  gray 
color  is  due  to  the  impurity  present,  the  analysis  showing  a  compar- 
atively large  amount  of  alumina  and  soda,  with  a  low  percentage  of 
silica.  This  is  probably  due  to  muddy  sediment  contained  in  the 
geyser  water,  which  is  left  with  the  silica  upon  evaporation.  The 
sinter  from  the  Solitary  Spring,  No.  Ill,  is  white,  opaque,  and  very 
light  and  porous.  It  is  the  sinter  resulting  from  the  desiccation  of 
an  area  of  algous  jelly,  such  as  that  abundant  about  this  spring,  and 
was jproduced  by  natural  causes.  Analysis  No.  IV  shows  the  com- 
position of  a  specimen  of  the  algous  jelly  found  at  the  Emerald 
Spring,  removed  from  the  water  and  dried  in  the  sun.  The  siliceous 
residue  of  this  jelly  is  light  pink  in  color,  very  buoyant,  floating 
readily  upon  water,  and  somewhat  hygroscopic.  The  air-dried  ma- 
terial lost  2.7  per  cent,  of  its  weight  when  dried  at  100°  C. 

Analysis  No.  V  is  of  the  straw-colored  moss  sinter  from  the  basins 
of  the  Asta  Spring.  The  structure  of  the  moss  is  perfectly  pre- 
served, and  much  of  the  sinter  is  composed  entirely  of  the  moss 
stems ;  but  other  parts  have  the  space  between  filled  with  friable 
white  silica,  with  occasional  botryoidal  concretions  of  light  gray 
opal. 

The  analyses  show  the  greater  purity  of  the  sinters  formed  by 
algse,  such  sinters  having  less  alumina  and  alkalies,  a  lower  percent- 
age of  water,  and  a  correspondingly  larger  amount  of  silica.  This 
greater  purity  is  probably  to  be  explained  by  the  fact  that  the  silica 
of  such  sinters  has  been  extracted  from  the  water  by  the  vital  growth 
of  the  plants,  while  sinters  formed  by  evaporation  contain  a  greater 
or  less  amount  of  kaolin,  generally  carried  in  minute  quantity  in. 
suspension  by  the  geyser  waters.  It  is  to  such  earthy  impurities 
that  we  must  ascribe  the  differences  in  the  analyses  of  Iceland  sin- 
ters made  by  different  chemists. 

The  physical  differences  in  the  unaltered  sinters  formed  by  evapo- 

'Peterm.  Geog.  Mitt.,  1862,  p.  266. 

3  Arnold  Hague,  Geol.  Ex.  40th  Par.,  1877,  vol.  2,  p.  826. 


672  FORMATION    OF    HOT    SPRING    DEPOSITS. 

ration  and  those  of  algous  origin  is  generally  quite  marked,  the 
former  being  translucent,  or  vitreous,  hard,  and  heavy,  while  the 
algous  sinter  is  opaque,  white,  and  often  chalk-like  in  appearance. 

SILICEOUS    SINTERS    FROM    NEW    ZEALAND. 

Through  the  courtesy  of  Prof.  F.  W.  Clarke,  a  small  collection  of 
siliceous  sinters  from  the  hot  springs  of  New  Zealand,  recently  re- 
ceived by  the  United  States  National  Museum,  has  been  placed  at 
my  disposal  for  examination  and  comparison  with  the  extensive 
series  of  sinters  collected  by  the  Yellowstone  Park  Survey  from  the 
hot  springs  and  geysers  of  that  region. 

The  New  Zealand  collection,  though  small,  contains  examples  of 
many  different  varieties  of  this  form  of  opal — the  result  of  diverse 
conditions  of  deposition  and  occurrence.  Most  of  the  specimens  come 
from  Rotorua,  the  sanitarium  of  New  Zealand,  situated  on  the  south- 
west shore  of  the  lake  of  the  same  name.  This  locality  was  long 
known  as  Ohinemutu,  the  name  of  the  Maori  village,  for  the  natives 
of  New  Zealand  utilized  the  hot  waters  of  these  springs  for  cooking 
and  bathing  before  the  discovery  of  the  islands  by  Captain  Cook. 
The  government,  appreciating  the  therapeutic  value  of  the  waters, 
has  leased  the  ground  from  the  Maoris  and  erected  extensive  bathing 
pavilions  and  bath  pools,  where  the  different  varieties  of  waters  may 
be  tried  under  the  direction  of  a  government  physician.  The  place 
was  formerly  the  starting  point  for  the  famous  terraces  of  Rotoma- 
hana  (the  "  Warm  Lake"),  which  were  destroyed  by  the  eruption  of 
Mount  Tarawera  in  1886.  But  Rotorua  is  itself  interesting ;  the  lake 
is  six  miles  across,  with  a  picturesque  island  in  its  center,  and  sur- 
rounded by  a  chain  of  blue  mountains,  while  the  ponds  and  wells  of 
hot  water  and  the  neighboring  geysers  of  Whakarewarewa  are  only 
rivaled  by  those  of  the  Yellowstone  and  the  famous  fountains  of 
Iceland. 

The  hot  springs  vary  in  character  from  the  clear  and  sparkling, 
albeit  boiling,  alkaline  siliceous  waters  of  Madame  Rachel's  Bath, 
supposed  to  renew  beauty,  if  not  youth,  to  chocolate-colored  and  ill- 
smelling  sulphurous  pools  and  strongly  acid  waters.  The  following 
analyses,  made  by  William  Skey,  the  Government  analyst,  show 
the  character  of  several  types  of  these  waters,  the  analyses  being  re- 
duced from  grains  per  gallon  to  parts  per  thousand. 


WEED.] 


SILICEOUS    SINTER    FROM   JSTEW    ZEALAND. 
Analyses  of  New  Zealand  spring  waters. 


673 


Madame 
Rachel's 
Bath,  alka- 
line, 174°  F. 

Priests1 
Bath, 
strongly 
acid. 

Hot  Pool, 

intense- 
ly acid, 
200°  F. 

SiO2,  silica,  free    

0.0838 

0  2630 

0  1957 

Na2SiO3,  sodium  silicate    

0  2601 

CaSiO3,  silicate  of  lime  

0.0605 

MgSiO3,  silicate  of  magnesium    .  . 

0.0155 

NaCl,  sodium  chloride  
KC1,  potassium  chloride    

0.9918 
0.0487 

0.5210 

NaSO4,  sodium  sulphate  .  . 
CaCl2,  chloride  of  lime  .  .   .....   . 

0.1685 

O.S748 

0.2643 
0.  1025 

MgCla,  chloride  of  magnesium  

0  0148 

AljClj,  chloride  of  aluminium  .  ,  .  .  . 

0  0617 

CaSO4,  sulphate  of  lime  
MgSO4,  sulphate  of  magnesia  .... 
A14(SO4)3,  sulphate  of  aluminium 
Fe2(SO4;3,  sulphate  of  iron  

0.1058 
0.0432 
0.0395 
0  1770 

H2SO4,  sulphuric  acid   

0  3160 

HC1,  hydrochloric  acid  

0  0521 

0  2315 

Total  

1  6633 

1  3821 

1  3931 

Free  HjS  

0  0425 

0  1355 

Free  CO»  

0  0308 

0  0177 

The  alkaline  water  of  Madame  Rachel's  Bath  is  said  to  deposit 
silica  quite  rapidly,  "a  ti-tree  twig  immersed  in  the  water  a  week 
or  two  resembling  a  branch  of  coral,"1  and  the  acid  waters  of  the 
Hot  Pool  form  mineral  mushrooms  of  muddy  sinter  in  the  shallow 
parts  of  the  spring. 

It  will  be  noticed  that  in  these  analyses  the  bases  have  been  com- 
bined with  silica  by  the  analyst,  who  states  that  the  conditions 
under  which  the  waters  occur  are  incompatible  with  the  existence 
of  carbonates,  though  the  analyses  of  Yellowstone  waters  show  that 
the  fixed  CO2  of  those  waters  must  exist  as  carbonates. 

The  siliceous  sinters  from  Rotorua  vary  from  pulverulent  deposits 
of  impure  silica  to  dense,  white  opal  sinters.  Two  of  the  specimens 
were  evidently  formed  about  spouting  vents,  showing  the  peculiar 
structure  and  beaded  surface  produced  by  the  evaporation  of  spattered 
drops  of  water.  Such  sinters,  to  which  the  name  of  geyserite  may  be 
most  properly  applied,  are  very  common  about  the  Yellowstone 
geysers,  occurring  often  in  beautiful  coralloidal  forms,  sometimes 
possessing  a  bright  pearly  luster.  The  New  Zealand  specimens  are 
parts  of  an  old  deposit  formed  in  this  way  and  consist  of  numerous 
little  pillars  formed  of  many  convex  layers  of  pink  and  white  silica, 
resembling  a  pile  of  minute  caps,  one  upon  another.  This  geyserite 
is  wholly  the  result  of  evaporation,  which  adds  film  after  film  of 
glassy  silica  to  the  surface  of  the  deposit,  as  often  as  wet  by  the 


1  J.  A.  Froude,  Oceana,  p.  236. 


9  GEOL- 


-43 


674  FORMATION    OF    HOT    SPRING    DEPOSITS. 

steam  or  spray  from  the  geyser.  An  analysis  of  this  sinter  is  given 
in  the  table  following  (p.  675).  Specimens  of  what  may  be  called  in- 
crustation sinter  resemble  a  handful  of  hay  crushed  in  the  hand 
and  coated  with  white  silica.  The  coarser  stalks  are  hollow  tubes 
with  rough  and  coral-like  outer  surface  with  the  finer  fibers  forming 
gnarled  and  botryoidal  masses.  Where  the  incrusting  process  has 
been  carried  still  further  the  thickened  coverings  of  silica  unite  and 
a  compact  sinter  with  but  small  cavities  results.  Such  sinters  are 
also  formed  by  evaporation,  on  the  exposure  of  the  water  to  the  air. 

Two  of  the  specimens  are  of  especial  interest  because  their  struct- 
ure indicates  that  the  algous  life  of  the  hot  waters  of  Rotorua  pro- 
duced siliceous  sinter.  This  action  of  hot  water  algae  has  been 
studied  in  the  waters  of  the  Yellowstone  springs  and  it  has  been 
shown  that  these  plants  abstract  silica  from  the  waters  in  their 
growth,  forming  a  mass  of  jelly  which  hardens  upon  the  death  of 
the  plants,  when  it  is  further  incrusted  by  silica  precipitated  by 
the  decaying  vegetable  matter.  In  this  way  vast  areas  of  sinter, 
often  many  feet  thick,  have  been  formed  in  the  Yellowstone  Park. 
The  specimens  from  Rotorua  show  two  distinct  forms  of  algous  sin- 
ter. The  first  is  that  produced  by  membranous  sheets  of  red  or 
green  algae,  resembling  certain  more  familiar  forms  of  seaweeds, 
common  not  only  in  the  cooler  waters  of  the  Yellowstone  but  in 
warm  waters  all  over  the  world,  being  described  as  "sheets  of  a 
slimy  conf ervoid  growth  "2  in  the  Rotorua  waters.  This  sinter  is 
creamy  pink,  showing  a  wavy  and  very  thinly  laminated  structure 
with  occasional  vesicular  blisters  lined  with  red  and  green  patches 
presumably  the  remains  of  algse.  It  resembles  so  closely  the  sinters 
formed  by  drying  the  algous  jellies  of  the  Yellowstone  springs  that 
a  similar  mode  of  formation  seems  probable. 

The  second  specimen  is  quite  different  in  structure,  consisting  of 
several  layers  of  fibrous  silica,  the  fibers  all  perpendicular  to  the 
layers  and  resembling  a  very  fine  and  short,  thick,  white  fur.  The 
exact  counterpart  of  this  sinter  occurs  at  many  localities  in  the  gey- 
ser basins  of  the  Yellowstone,  notably  about  the  Prismatic  Spring 
and  the  overflow  channels  of  Old  Faithful.  It  forms  over  one-half 
of  the  section  of  15  feet  of  sinter  exposed  in  the  crater  walls  of  the 
Excelsior  Geyser.  This  sinter  we  know  to  be  the  result  of  the 
growth  and  incrustation  of  little  algae,  which  form  a  cedar-colored 
(Caloihrix  gypsophila  Kg.,  or  olive  (Mastigonema  thermale)  slippery 
coating  on  the  surface  of  the  deposit.  The  analogy  is  so  perfect 
that  there  seems  but  little  doubt  that  the  New  Zealand  sinter  is  the 
result  of  the  growth  of  similar  or  allied  algae. 

Other  specimens  of  the  hot-water  deposits  of  the  Rotorua  Springs 
resemble  blocks  of  diatomaceous  earth  and  vary  from  a  loosely  com- 

8  Skey  :  Trans.  N.  Z.  Inst.,  vol.  10,  p.  433. 


WEED.] 


ANALYSES    OF    ROTORUA    SINTERS. 


675 


pacted  mass  of  pulverulent  silica  to  a  dense  and  almost  jaspery  sinter. 
The  impalpable  particles  composing  this  material  are  angular  and 
consist  almost  wholly  of  milky  or  transparent  glassy  silica.  Analysis 
No.  Ill  of  the  following  table  shows  this  substance  to  be  a  mixture 
of  clay  and  silica  of  the  same  composition  as  the  material  incrusting 
logs  immersed  in  the  siliceous  waters  of  the  Yellowstone,  and  often 
lining  the  hot-spring  bowls. 

The  following  analyses  of  three  types  of  the  Rotorua  sinters  were 
made  by  Mr.  J.  Edward  Whitfield  : 

Analyses  of  Rotorua  Sinters. 


I.-Gey- 
serite. 

II.—  Algse 
sinter. 

III.-Pul- 

verulent 
silica. 

Si  Oj,  silica  

90  28 

92  47 

74  63 

A12  O3(+FesO9)  

3.00 

2.54 

15  59 

Ca  O,  lime 

0  44 

0  79 

1  00 

Mg  O,  magnesia  

Trace. 

0  15 

Trace 

Na2  O.  soda  

0  30 

K2  O,  potash  

1  02 

Ignition  

6.24 

3  99 

7  43 

Total  

99  96 

99  94 

99  97 

The  remaining  specimens  from  Rotorua  consist  of  a  hot  spring 
sandstone,  produced  by  the  cementation  of  particles  of  rhyolitic  glass, 
feldspar,  and  quartz  by  the  siliceous  waters  of  the  springs.  The 
fragments  are  uniformly  angular,  well  assorted  in  layers,  and  bound 
together  by  transparent  or  milky  silica.  The  latter  usually  forms  a 
very  small  part  of  the  bulk  of  the  specimen ;  in  only  one  case  does 
it  sheath  the  grains  in  a  coating  of  silica,  and  form  a  noticeable  part 
of  the  deposit.  Under  the  microscope  thin  sections  show  no  traces 
of  enlargement  of  the  crystal  fragments.  Though  a  true  hot  spring 
deposit,  this  material  can  not  claim  the  name  of  siliceous  sinter.  Two 
of  the  specimens  contain  very  showy  leaf  impressions,  but  the  de- 
tails of  veination  are  not  preserved,  and  the  woody  tissue  is  absent. 
A  white  "mineral  wool"  occurring  in  other  specimens  of  this  nature 
is  perfectly  silicified  woody  fibre.  Such  sandstones  are  common 
about  the  hot  springs  of  the  Norris  and  Shoshone  Geyser  Basins  and 
other  localities  of  the  Yellowstone  Park,  where  they  are  formed  by 
the  cementation  of  material  washed  into  the  springs  from  the  sur- 
rounding slopes  of  disintegrating  or  decomposed  rock. 

Besides  the  sinters  from  Rotorua,  the  collection  contains  a  few 
specimens  from  the  famous  White  Terrace.  This  sinter  opal  closely 
resembles  the  deposits  of  the  Coral  Spring,  whose  water,  like  that  of 
the  lost  White  Terrace,  is  opalescent  with  silica,  which  is  carried  in 
pseudo-suspension,  and  which  rapidly  coats  articles  immersed  in  it. 
Two  jaspery  sinters  from  Whangerei — a  seaport  about  eighty  miles 


676  FORMATION    OF    HOT    SPRING    DEPOSITS. 

north  of  Auckland— are  very  beautifully  colored,  in  red  and  green 
bands,  but  are  of  no  especial  interest. 

No  information  is  obtainable  relative  to  the  comparative  abundance 
of  the  different  types  of  sinter,  but  the  prevalence  of  acid  and  com- 
parative scarcity  of  alkaline  waters  shown  by  the  list  of  springs  pub- 
lished by  Dr.  Hector  leads  to  the  belief  that  algous  sinter  forms  a 
smaller  proportion  of  the  siliceous  deposits  than  it  does  at  most  of 
the  geyser  basins  of  the  Yellowstone,  where  the  waters  are  chiefly 
alkaline.  The  general  character  of  the  springs  shows  that  Rotorua 
resembles  the  Norris  Basin  more  closely  than  any  other  locality  in 
the  Park. 

SUMMARY. 

In  the  light  of  the  knowledge  gained  in  the  Yellowstone  Geyser 
Basins,  the  observations  of  Prof.  W.  H.  Brewer,  referred  to  in  the 
first  part  of  this  paper,  acquire  a  new  interest,  and  it  seems  quite 
probable  that  the  gelatinous  silica  containing  algse  which  he  found 
at  Steamboat  Springs,  Nevada,  may  resemble  that  so  abundant  in 
the  hot  waters  of  the  Park,  and  that  a  part,  at  least,  of  the  siliceous 
deposits  found  at  Steamboat  Springs  may  have  been  formed  by 
algous  life.  The  fibrous  sinter  from  the  Azores,  called  Michaelite, 
occurring  about  springs  where  algous  vegetation  was  found  to  be 
abundant,  certainly  suggests  a  possible  like  origin.  The  data  acces- 
sible are  far  too  meager  to  hazard  any  conjectures  as  to  the  nature 
of  the  Iceland  or  New  Zealand  sinters,  but  the  occurrence  of  algae  in 
these  waters  is  significant  in  this  connection. 

It  is  believed  that  the  facts  recorded  in  the  preceding  pages  estab- 
lish- 

1.  That  the  plant  life  of  the  calcareous  Mammoth  Hot  Springs 
waters  causes  the  deposition  of  travertine,  and  is  a  very  important 
agent  in  the  formation  of  such  deposits. 

2.  The  vegetation  of  the  hot  alkaline  waters  of  the  Geyser  Basins 
eliminates  silica  from  the  water  by  its  vital  growth  and  produces 
deposits  of  siliceous  sinter. 

3.  The  thickness  and  extent  of  the  deposits  produced  by  the  plant 
life  of  thermal  waters  establishes  the  importance  of  such  vegetation 
as  a  geological  agent. 


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(415)  642-6753 
1-year  loans  may  be  recharged  by  bringing  books 

to  NRLF 
Renewals  and  recharges  may  be  made  4  days 

prior  to  due  date 


DUE  AS  STAMPED  BELOW 


APR      I  1992 
APR  29  1992 


LD  21-10m-5,'43 (6061s) 


THE  UNIVERSITY  OF  CALIFORNIA  UBRAR1 


